Future, like almost all acrylic coatings, dries to touch rapidly, but cures relatively slowly and continues to outgas its solvents almost through the curing process. Under humid conditions, this can take a distressingly long time. Placing Parafilm over the uncured coating traps the solvent near the coating surface, softening it.
When masking over Future with Parafilm, Frisket, or any other impermeable medium, either wait longer, or force cure. If you have access to a forced air food dehydrator, they are perfect for this. Otherwise, cut vents in the top of a largish cardboard box, place your model and an incandescent lamp about a foot apart, and put the box over them. The box has to be large enough to leave at least a foot of space above the lamp, which should be in the 40 to 60 watt range. A small fan blowing out of the box is a good idea, too. Make sure that the lamp cannot come in contact with the box or the model. The temperature you want is about 105 to 120°F. A few hours should do it. Do not leave the box unattended or where small children or animals can get to it. (Cats are particularly dangerous, as they may decide to nap on the top of the warm box.)