I let future dry for at least 24 hours between coats. I use future on a/c to seal the decals and before I apply an oil wash over acrylic paint. My paint process goes like such:
1. apply paint, let dry 24 hrs.
2. apply 1 coat of future so decals have gloss coat to set on, let dry 24 hrs.
3. apply decals, let dry/set
4. apply a light coat of future to seal decals, let dry 24 hrs
5. apply a second light coat of future, let dry 24 to 48 hrs. (if the model will be handled a lot in step 6 I wait 48 hrs to be sure the future is totally dry, if I can wash and weather the plane without having to move it too much I wait 24 hours)
6. apply wash and weathering
7. final coat, future if the model is to have a gloss finish, Testors acrylic flat if the model is to be dull.