Wet sanding, final grit?

[seriouswood]

Sanding down some bumper covers (Miata) and a metal panel. What should be my final sand paper grit when I am finishing my sanding and ready for paint. Is it the same for the plastic bumper cover vrs metal panels?

[seriouswood]

also, I am just sanding the orig paint, not taking down to bare surface. DO I really need to prime in this case? Isn't the orig paint sanded like primer?

[silvercert]

Sanding down some bumper covers (Miata) and a metal panel. What should be my final sand paper grit when I am finishing my sanding and ready for paint. Is it the same for the plastic bumper cover vrs metal panels?

Well im painting this weekend and im going with a 150/220 then 320 on the existing paint. I will prime what is not white (PO two toned it) and then sand again (the primed spots) with 320/500. I will feather in the existing white with the primered spots. Im no expert and this is my first time taking on this big of painting but im all for it and excited as can be to do it. I have faith that it will turn out great. I've prayed hard about it.

[Austin 4x4]

as long as the original paint is in good condition you dont need to prime. finish sanding with 500 or 600 before you put on the topcoat and you should be good.

[ABN82MP]

I hit mine with a 400 before I sprayed it. Finish came out very nice:

http://is7.itookthisonmyphone.com/media/00036/8d5715b9-15a6-4a80-bbb3-3fbdb9d566e0/2bcdbd2b-01f3-4701-9879-61b91e26507c_568x426r0.jpg

[babywag]

I wouldn't go higher than 400...

Be sure you use a quality plastic friendly paint or additive, or you're wasting a lot of time & your $$$.

You should use a sealer over the original paint as well to promote adhesion.

Most paints have pretty detailed prep information, unless you're using rattle cans?

[Chrome]

It depends if you are going with a dark color or not. If a lighter color is used then 400 will be fine but if you are going with a darker color then I would use 600 for the final sand. On darker colors you can see very light sand scratches after the paint fully cures especially if you only apply 2-3 coats of paint. As for the factory paint it will be fine as a base just go easy with the first couple of coats to make sure you get no reaction from the new paint. I've seen paint do all sorts of ugly stuff when new is applied over the old especially when done in heavier coats from the start.

Good luck!

[seriouswood]

well what I have is a miata with a single stage green front bumper, red single stage painted rear bumper. And a metal mid panel in back that is white and a front fender that is primed black already. I am painting parts Silver to match rest of car which is base/clear coat thus same for the parts I have to paint.