A dry mounting press just isn't an option -- no room for it, and they still go for a few hundred dollars on E-bay, just not worth it solely for flattening prints. How about a clothes iron on a steam setting?
For FB paper, I've found that normal air-drying on racks (overnight), and then pressure (photos between sheets of blotting paper, stack of book on top) is sufficient to make a proper flat print. If you do it this way, it's good to take the print out of the stack every once in a while to make sure that any humidity still trapped in the photo is dried out. Slow, but foolproof.
If you dry with heat, it is of paramount importance that you be able to apply pressure at the same time. A drymount press should of course give you good results, but a clothes iron at low heat, pressed onto a sandwich of blotter/photo/blotter gives good results as well. But you really need to make sure you apply consistent pressure.
Most curling problems I've had were due to a bad combination of quick drying / lack of pressure. The old driers with a curved bed and a cloth covering can be particularly bad in this respect: they dry too quick, and don't give enough pressure. They can be useful to accelerate initial drying, but you have to monitor them closely, otherwise your edges will curl.
You can use acid-free watercolor paper if you can't find blotting paper. As long as it leaves no fiber in the gelatin, no texture marks, no chemical residues, and can absorb water, you should be fine.