When I proof, I only fix them for 30 seconds. The proofs then get a first wash and are hung on a line--NOT put on the drying screens.
The whole proofing process is quick--two to three hours for a couple of hundred new 8x10s. The point at this stage is to see what you saw on the ground glass--not to agonize over getting a great print. All proofs get made on the softest grade of paper to show all information in the negative. When you go to make finished prints you can usually easily tell what grade of paper to use by the relative degree of contrast on the softest grade of paper.
Hope that is helpful.
Michael A. Smith