Re-finishing a Scoche DD kit, quick question.

So, Sears sent me a gray Scoche HU kit instead of a black one, and instead of sending it back I decided just to sand it down and re-paint it myself.

I used very fine sandpaper and sanded it as best I could, rinsed it down good and am waiting for it to dry.

I got some Krylon Fusion, Satin Black, that bonds plastic, and I was wondering if I'd need a sealant after I paint? Also, would I need to prime it? It says no sanding (oops) or priming, but is that right?

If I do need a sealant, what's the best kind of sealant that would best match the satin finish of the little panels next to the HU interface?

Thanks if anyone can help.

 

I couldn't find any black ones at Amazon. Plus, I had the sandpaper already and I kind of wanted to practice.