One tip that I found to be very useful is to use a document hole punch to make loads of small circles of very fine wet and dry paper. These can be stuck to the end of a pencil and used to rub down very small areas.
The other thing to remind oneself is that it's very easy to spot imperfections when you're concentrating hard and staring at it from a range of 6 inches, but when you're stood up and looking at it from a range of 6 feet it looks fine.
