Need Help With My Clearcoat

I have a 1992 F150 that I have just painted. Problem is that I painted it outside and little pieces of crap have landed in it (wasn't windy when I started). Also I thought I had enough clearcoat to give it 4 coats. I only had enough for 2. Can I wet sand and apply more clearcoat later? I sure would like more on it. Or maybe someone can point me to a better forum to post this on. Thanks.