what is the proper grit for wet sanding a primered fender? to make it look smooth by getting rid of those rougher blotches you can see with any primer?
disregard that comment, i dont know what i was thinkin.... and no i havent heard this from anyone finer...
You can use a heavier grit on primer, because the top coat is going to fill in the little scratches. If you just want to knock down the orange peel, I'd suggest a DA sander dry. Primer doesn't have to look good. Just have the right shape. I've seen a DA used dry on top coat even to knock down the orange peel. After that it was wet sanded with 600 to get rid of the scratches, then rubbed, buffed etc. Looked great. Nice flat shiny surface, just like a mirror.
The smoother the prep, the smoother the top coat. I would not use anything less than 400. Sanding scratches can and do show through. Wet sanding is the only way to go.
If it is the final primer coat and your finish color is going over the top of it.400 to 600 grit.If you are blocking and working the surface 180 to 220.Remember paint does not fill dents scratches(primer/filler)is the exception or holes.Use a good epoxy primer for your final prime coat so as to prevent bleed through or blemishis(sealer is even better) And listen to what mavaholic said(its the golden rule)
Lacquer primers absorb water like a sponge and they really shouldn't be wet sanded. Luckily, they sand easily dry with 400-600. I used some 2K Urethane primer. Stuff fills in about every little scratch and sands easily..and won't absorb water as readily as lacquer will. As far as sanding, you can block it with 180 to knock it down. Then go to 240, then to 320 and final sanding before applying color can be done with 600 wet. That should give you an excellent base for the color to lay down on and usually if the color is applied correctly, you wont have much color sanding to do. If you wet sand 2k urethane primers, it's a good idea to let the car (or part) sit in a heated area over night to evaporate all the water. Otherwise you'll end up usually re-doing it.
