Nasty.....I've had good/bad results with Future runs. I've had some of the runs completely dry and go hard (easy to rub out with 1500 wet and dry) and I've had some runs stay kind of gooey, even weeks after airbrushing.
If you're lucky and the run dries hard, then use very fine sandpaper (like 1200 or 1500) and carefully rub in one direction using NO WATER (I've had the Future go a little soft when wet sanding), until the run is removed. Then when the run is removed, re-coat with Future to get rid of the sanding marks.
If the run stays tacky, carefully shave off the high spots on the run, allow 24-28 hours to dry, then sand (dry) and re-coat.
That should fix your problem. Make sure you dust on several light mist coats, allowing 4-5 minutes inbetween before you hit the model with a wet coat.
Good luck,
LeeTree