Clear coat rough after new paint

So someone rear ended me last week. It was minor and the bumper just needed some sanding and repainting. Over the weekend, I removed it, sanded it, used some bondo on the parts where the paint was cracked, sanded it again. Then i put a layer of primer and sanded it again. It was a good coat so I just had one. Everything looked good. Then I applied two coats of paint. It still looked good. No dripping, nothing bad. I used a compressor and gun to do this btw. Then I applied two medium layers of clear coat. It all looked good, but when I came back yesterday to put it back on the car, the clear coat is not shiny and smooth like the rest of the car. It was, however, shiny the night before. I don't know what caused this. It's my first time working with this type of equipment and really painting. I had my uncle help me out and he said it just needs to be buffed out once it heals. But I don't know, it looks weird to me. It has a rough surface, kind of grainy. Any help is appreciated.

- MV