Don't' dry them too fast. If all else fails - get a dry mounting press 
The curl happens because the gelatin side tends to dry faster than the paper side. As far as I know, there are only two cheap non labor intensive ways to get this fixed.
First is to dry the prints in a blotting book. Since the book is held flat by a strap or a rubber band, the prints don't curl. Also the slow drying process helps a lot. This gives very matte prints.
The other is glass drying. You squeegee the print face down on a very smooth and clean sheet of glass and let it dry until it unsticks itself from it. Once it's on the glass, the only way to remove it is to wait until everything is dry... else the emulsion will stay stuck and becomes a real b**** to clean!
