Prior to painting a model I’ve always heard one should clean the parts to clean off the residue on the plastic. I’ve never done this before and have always used Model Master Enamels with no problems. I’ve just switched to Gunze Sangyo and Tamiya Acrylics. So my question is this: How do you clean the plastic??? Do you leave all the parts on the trees and let it soak in soap & water or alcohol? Do you rub them? What’s the best and/or easiest way to clean them so the acrylic paint sticks good?
Most people use soap and water, I prefer alcohol. The goal is to get the mold release oil off and either will work fine. IMO alcohol dries quicker and that’s why I prefer it.
Regardless, acrylics are still never going to adhere to bare plastic as well as enamel or laquer. They adhere pretty well, but still not as strongly as other types of paint. I prefer to spray a coat of enamel primer prior to using acrylics.
i usually dont bother washing the parts while their on the tree, coz they still have to prepped and handled… i was my kits when all the construction is done ( or as much as possible), and then wash it out… to clean the kits i have a film conatainer full of liquid soap. i use a large flat brush, dunk it in da soap, then work it over them model, then i rinse it off with warm water (not too hot!!) while still working it with the brush, to help get the soap off… i then shake off any excess water, then place it in my drying box to air dry…
i avoid using a towel or something similar, coz this will place dust, lint, fibers, whatever! 
on the model… if ur in a hurry, use a hairdryer or ur airbrush too speed it up…
hope this helps!!!
also, as scott said, when using acrlys, a good primer is a must…use a enamel or laquer based one (im using mrbase white 1000(lacquer based) atm, with great results…
heres a faq for using it http://www.swannysmodels.com/Surfacer.html
i just clean my models with soap and water. i hardly use primer though, as i think it covers up detail too much. but then again, primer gives your paint excellent grip.
I agree with Tom on that one. I clean my parts right before I paint them (literally right before, usually only a couple of minutes) and then blow everything off with compressed air. I don’t think washing parts on the tree accomplishes much unless you are going to wear gloves during assembly, and some people do use gloves.
Use thin primer and only a thin coat, just enough to get even coverage. A single coat of primer covers up no more detail than a single coat of the base color, and it frequently allows the base color to be sprayed with fewer coats.