Removed the overspray and other gunk with 150 wet/dry; then sanded with 320
wet:dry

1. Should I continue on with finer paper ?
2. What paint is recommended ?

Nowadays you can get rattle can paint that sticks to plastic. I would test a semi gloss clear, or maybe a semi gloss black. I stay as clear of rustoleum as I can because I have problems with lifting on second coats, directions followed or not.
I have to say I am impressed by your diligence, but not too surprised.

Jim,

IMHO I'd continue down to 1000, 1500-ish or 2000 until you get a base smoothed to close to what was original, but suggest either Satin or Matte black as closer to original finish (rather than semi-gloss, which will be too shiny & show flaws more).

And I agree with using one of the plastic formulated auto paints - SEM, Eastwood, etc. I've had similar problems with Rustoleum, & not just on plastics.


Tom
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Thanks for the tips There a place in Costa Mesa on 17th that sell the SEM matte etc

I’ve done the clips and will take the plastic down to 1000 grit

I see scratches.
Keep sanding
You should not see scratches, more of a dull hazed look.
Then paint it.

Honestly, if you do it right, at 1000 or 2000 you could buff it and may not need paint.

You should be able to sand and polish back to the original sheen. It will take more time though.

Soda blasting also does a good job of renewing the surface...and makes it easier to get in between the letters. Not sure how it will work on a box that’s already been sanded, but I’d imagine it would do the trick. Just be careful your pressure and distance aren’t too aggressive.

That scratch doesn’t want to come out; I’m going to look for a replacement piece. Some of the fresh air systems have been completely removed and maybe I can locate a front piece in better condition.....