Another one of my personal techniques...I recommend prepping the bare plastic body by scrubbing with Comet, a toothbrush and plenty of hot water. Sanding will NOT get in all the crevices around details (I've looked at the surface under high magnification to verify this), and it also tends to blunt and soften the crispness of details.
If you have heavy bodywork to do, roughen the surface under where filler will go with 180 grit paper, and make sure you mix your two-part filler correctly. Poor mixing technique and poor surface prep is responsible for the adhesion problems some folks have with fillers. Try to avoid putting two-part filler over primer. My orange Chevelle above has MAJOR bodywork in the quarter panels, as the top is chopped 4 scale inches.
After major bodywork is finished and very closely shaped, I shoot two coats of Duplicolor or Plasticoat (both the High-Build varieties) primer, letting it flash completely in between coats. I'll often bury minor inperfections on local areas in more primer, or if the problems are too much for primer, a little ONE-PART glazing putty, which is simply very thick lacquer primer.
LET IT DRY COMPLETELY. It WILL SHRINK as it dries. I sand out imperfections with 600 grit wet, and look over the model VERY carefully...then go back and rework any remaining problems. Again, LOOK AT YOUR WORK VERY CAREFULLY AND CRITICALLY, as paint will NOT cover or hide bad bodywork.
My final 600 wet sanding of the primer leaves a flat and smooth surface with NO orange peel. I usually shoot lacquer or automotive-basecoat, one medium wet coat of paint first, as I personally find that shooting a mist coat first adds to orange peel buildup. A medium-wet coat will also give you sufficient shine to show up any remaining flaws. Nice thing about lacquer or automotive-basecoat colors is that they dry quick, and any tiny imperfections can be sanded out before you go any further. Enamel has to be allowed a long dry-time, or stripped.
Depending on the topcoat color and the final primer color, three to six coats of color usually get it. I've learned to shoot the color wet enough so it self-levels but doesn't run, and usually requires no sanding prior to clearing. Solid color lacquers require no clear and can be sanded up to 12,000 grit wet and polished. Aotomotive basecoats, Testors basecoats (the two-part lacquer system) and metallics all require clear.
DO NOT sand metallics or pearls inmmediately prior to clearcoating. Sanding of these without recoating with more color is virtually GUARANTEED to leave noticable blotchiness under the clear. If you have a flaw in metallics or clears, let it dry hard, sand the flaw out and then CAREFILLY re-spray the affected area with color to hiding, then shoot your clear. I use three coats of model-car lacquer clear, minimum, to allow sufficient material for wet-sanding and polishing without cutting through the clear and screwing the color.
Edited by Ace-Garageguy, 10 February 2013 - 05:02 AM.