I think I've been doing something neat I should tell you guys about.
I use automotive tac rags when I model. I use them mostly to clear dust before priming. But, I also use them in between coats to smooth coats.
I use a lot of Krylon stuff. Sometimes, when using automotive primers, there might be a "gritty" finish where I've kept my coats light due to preshading. Ten years ago, I would have stripped the model and started over. But, for the last few years, I've been using tac rags.
For a gritty paint job, be it a color coat or a clear coat, I'll simply let the coat thoroughly dry, and repeatedly wipe in the direction of the airflow. This smooths and blends the coat, and buffs away the rough pigment that dried before hitting the surface.
Sometimes if my colors over preshading aren't subtle enough and I can see the individual drops of paint, I will perform the same process. It works wonders in these cases too. When finished, the coat actually has a satin sheen to it. It's similar to buffing pastels or blending oil paints.
Also, clear Krylon flat can be gritty sometimes. Tac rag buffing seems to do wonders with this as well. Be mindful, though, of any pastel weathering you may have already done.
I think it seems to help with gritty Future, but to be honest, I haven't had a Future kaboom in a while.
The one caveat to all of these examples is light, misting coats. All the tac rags in the world won't fix a drowned model.

For those that don't know, tac rags are slightly tacky rags for removing dust prior to painting. They're about the consistency of gauze or cheesecloth.
I hope this helps.
Kenny