Paint and Body What to use to clean up/prep painted surfaces before painting

So I fully restored my quarter window glass trim a while ago and now that my cars back I went to put them on. Looks like they got damaged sitting in my garage so I went to spray a fresh coat of paint on them. I scuffed them and sprayed them with a prep spray I have but I guess it’s not meant to go on paint and it thinned out the paint and made it all gummy. Now there’s spots where the surface is all rough from where I first put the rag on it.

What grit sandpaper should I use to smooth out the messed up parts with and what is the correct spray to use to clean an already painted surface before painting that wont thin it out like mine did?

rednotch said:

What prep spay did you use, looks like the paint had a reaction to it. Sem trim paint is lacquer, it does not like solvent based cleaners. I'd use a heat gun to dry out any solvents, scuff with 300 -400 until it smooths out, wipe down with a water based prep or even dawn and water with a grey scuff pad then reshoot when dry. The set on my red car I did around 20 years ago now and still holding up fine. Used ever coat glaze as a filler and crest trim coat back them. Did more then a few with sem trim coat since then.

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Used a can of duplicolor prep spray I had. Ok sounds good I will do that. Thanks.