Brush cleaning....

I just tried it on a whim. It removes some of the gloss. Also on Krylon, I give a lot of what I make away to people who don't care how it looks so using whatever's cheapest and will keep the various paints and pigments on will do.

I never heard of adding a flat base to Future.

My go-to clearcoat is Rustoleum brand clearcoat in rattlecan. Just spray in 2 or 3 light coats.

Oh yeah - stay away for all Krylon brand paints. They're garbage.

Ammonia makes quick work of eradicating all traces of Future from brush bristles (and everything else). You can use Windex (or any ammonia-based glass cleaner)

I'm far from experienced but if it's something I don't like much or care about, I'll use some cheap off the shelf rattlecan topcoat to finish. Just enough to seal in paint and details.

If it's something I like I'll use future or future with some tamiya flat base in it.

If I want to display it, I buy some nicer hobby-specific topcoat.