If possible push down on the pup to relieve a bit of pressure from the screw. Then while holding the pup down, completely unscrew the screw. Run the threads over a dry bar of soap and reinsert the screws in the pups. The soap will lubricate the screw and it should be much easier to crank down.
This will work but if you are a wood worker and have wax, which if you are a wood worker you will, use that.

