Here are some other tips for painting.
Washing - You can usually get away without washing but as Zero Pilot mentioned. It it’s better to wash pieces first for best results. If you do, make sure it dries thoroughly before painting. If you want to speed up the drying use an air can or a hair dryer on low and cool setting. Avoid using a cloth since little strand of fiber can stick to the plastic.
For small pieces like the A&A units you really don’t need to use a primer. I would use it only if you wanted to paint a dark colored unit with a light color. If you don’t, it just might take an extra 1 or 2 coats of paints.
If you can, always paint the units before you break them off the tree. Trying to paint them as separate pieces can be more difficult.
Airbrushes will always give you a better finish but you can still get a nice finish with spray cans. Here are some tips when using spray cans.
1. Make sure your can is warm (room temperature). If it is cold put it in a bowl of hot water to warm it.
2. Shake it well.
3. When spraying, do not hold it too close. Spay can paint can sometimes be thick and if you’re too close you can have a layer of goop instead a nice coat of paint. For best results it’s always better to start farther way and apply a 2 or 3 light coats of paint rather then doing it in one coat. Also, if pieces are not on a tree, you can blow them all over the place if you are too close. You’re more prone to do this with an airbrush than a paint can.
4. Practice painting something else first so you can see what works best.