I've always apply my clear coats on the same day, sometimes 3-5 coats and then put the body away to gas out. Now, if a few days later I feel it needs another coat, I wet sand the body, and then hit it up with one or two more coats . . . that usually works.
I would recommend that same process if you have cleared your body and a couple of weeks later you want to add more clear, etc . . .