Bodywork on Plastics

[Cutlass Queen]

Finally starting the body work on my 85 Iroc Z and was wondering what is the best way to treat the plastics for prepping it for paint? Do you use a finer grit sandpaper or would that cause scratches in it? I've never attempted prepping plastics for paint so it's a whole new thing for me, suggestions would be greatly appreciated!

:confused

[Wagonbacker9]

Same as metal, just have to be more careful blocking, and make sure you use a compatible filler and primer.

[Cutlass Queen]

What would you recommend for the grit of sand paper so it doesnt cause any gouges in it? 320?