I just found this post by stevet(the one who did my parts) over on FTW and thought it would be useful here in the "how-To's".
I thought that I would post this up for those of you that would like to try painting your parts or have thought about having someone else paint your parts.
Here is my advise:
(1) Don't trust any bodyshop to prepare them for ya like I would because their only intent is to get the job done a.s.a.p and because of that they may not clean, sand and prep them as good as it should, so I will explain ways you can guarentee that what ever paint is sprayed it will stick.
(2) If you spray it your self, the types of spray paint that you can buy over the counter is the one's in the can but remember you will never find paints to match the color coded paints of your car unless you order them on-line or you know a paint shop (Jobber) that will mix to code and sells them in a aerosol application. Even then sometimes you cannot predict by how much pressure the aerosol spray lays out the paint when it hits the surface causing the paint not to flow and gloss especially if it is a solid color.
You do have 2 choises, try painting it yourself using spray can paints or have a pro paint it for ya using automotive paints. There is 3 draw backs to using aerosol spray paints. A. You can't always find a place to order or mix the paint in that application to your exact color code. B. It will not flow and gloss like automotive paints will. C. It is not as durable and long lasting as automotive paints.
The most important thing to do before any painting is involved is preparation, and in this case we are talking about any plastic part that is hard and not easily bendable like dash parts, outside mirrors, cowls, fibreglass parts bumpers ect.... Either way you go as far as spray can VS pro automotive paints the preparation is the same. Here is what I do.
1. Buy some good mechanics hand soap (The kind with the grit in it) and some double ott #00 steal wool pads, the larger the pad the better. Using a lot of water get the part completly wet and taking the steal wool and dipping it in the hand soap scrubb the part very thoughly and make sure to get every crevise and corner. Rinse well and let dry in the sun, after drying you can see any spots that you may have missed and re-do scrubbing with the materials and let dry again and check. The hand soap and steal wool serves 2 purposes the hand soap washes and get's all grime, oil, dirt & bugs off the parts and rinses well while sanding the surface very fine without damaging or fraying the plastic, and the steal wool does exactly the same assuring fine sanding of the surface.
Some of our Ford plastic parts that have texture have different charactaristics in the compounds in the plastics where you can sand the texture off with 80 grit sandpaper. For example: Back window surrounds and some interior parts are a harder plastic, where the plactic of a lower OEM valance are soft. The harder plastics can be sanded with 80 grit where as the soft plastics will fray.
If you choose to sand the harder plastics with 80 grit, sand down the texture till flat (Test first a small spot) then sand with 150 and 220 and primer as usual. Let dry overnight and spray a mist of black can spray paint to mist on a check coat. Wet sand with 400 grit wet/dry sandpaper using water at all times to rinse off residue and make sanding easier. Sand till all the black check coat sands off but try to be careful not to sand through the primer back down to the plastic as you will have to re-primer that spot. Paint as usual.
On Plastic urathance bumper or valances you should use 400 grit wet/dry sandpaper using water. Use the same procedures by rinsing and letting it dry to see where you missed spots. In very tight corners you can use the steal wool and handsoap as well.
2. Once you see that every nook and cranny has been scrubbed and sanded, once rinsed and dryed it will look hazy and dull and is ready for primer.
At this stage if you want to paint it yourself you will need a few things that can be bought at Autozone & Pep boys and some automotive paint store's. They have a special flexable primer promotor at $5 a can and depending on how many parts you have you may need 3-4 cans. The same with the primers of the same brand but make sure they say flexable primers for plastic parts. Spray the promotor first as directed let dry 2-3 minutes on the last coat and then it's ready for the primer as it need to be sprayed wet on wet. Sweep side to side and don't stop in one spot for it will build up and run. Anything you don't use you can return for a refund.
If your going to allow the texture to show through then your need not sand it smooth once the primer is dry, purchace a scuff pad (resembles a scouring dish pad) but it's made to scuff paints and primers There is red and grey, I prefer the grey. After scuffing the surface trying not to scuff through the primer wash it down with water to rinse all dust, dirts, hairs, ect... and let dry. Try not to touch the paintable surface with your fingers because you have natural oils on your hands that will ruin your paints and paints have a tendency to separate from an oily spot, they call fish eye's ?
If you are going for a flat smooth finish with no textures showing through you must sand the prepared surface with a wet and dry 360-400 grit sand paper using water at all times. Rinse and let dry to see how far you have sanded and repeat if nessassary. It is not nessessary to sand all the way flat the plastic surface only a little. Additional coats of primer is nessessary to build up the surface to hide the texture, after primer is dry sand with 400 grit Wet/dry sand paper using water, rinse and let dry and see if you can still see the texture, if so repeat sanding or build up with more primer in those spots, let dry and repeat sanding till no more texture shows though.
Then you are ready for painting. Make sure that where you are painting there is no wind present to blow dust in your paint job and if you are painting outside in the drive way, water down the driveway to keep the dust and lint down. Best weather conditions to spray would be around 65-75 degress.
Spray can paints can be hard to get the kinds of results that make the paints gloss but you must make sure that you start off with a light even coat, let dry 15-20 minutes and do a second wetter even coat. Wait 15-20 minutes and follow with a 3 or 4 very wet coat and make sure to make it even coats all around. For metallic colors you would also follow with a clear coat. 2 light coats followed by 2 wet coats letting each coat dry 15-20 minutes between coats. followed by the last wet coat.
If you have a pro paint it be sure to prepare it as instructed above to insure that what ever paints they spray it will stick. You do not at this point have to purchase any paints or primers they will do that. But make sure to mention that you want flex additives added to the primers, and all paint stages to be sprayed on your parts.
Good luck and if you have any questions email me direct.