I had to fix a part of my car with a rattle can and it came out uneven. Meaning some areas are shinny while some are kinda flat. I was wondering if the clear coat will get rid of this or if I need to do something before? thanks in advance.

 

Try sanding the area with 1200 or close grit then step up to 2000 or similar. After that a course polish then a swirl remover, hand polish. That might bring up a shine you can deal with. If you want to clear, you want to prep the entire panel.