Future is good stuff, as all these other fellas have said. It's very flexible and forgiving, as well. You can spray it, or brush it. You can use it for to spruce up a canopy, or as a base for decals.
If brushing, most brush marks will work themselves out as Future is "self-leveling". Also if you brush it, it may take on a milky appearance. DON'T WORRY! That should go away.
If spraying it, thinning is not necessary. But if you ever have a need to do so, water will work fine. Alcohol does funny things to Future, so I'd steer clear of it. I haven't tried any other thinners for it because, as I said, it doesn't really need it.
Future is way-cool in another respect. I'm a brave builder sometimes and have been known to try some weird things now and again.
When I'm laying down a clear for decaling, I sand the model to get rid of any high spots, dust or other "schtuff", using the finest grit available. (Usually the coarsest part of a tri-grit sanding stick such as the one Squadron offers) This will, of course, mar the finish as well as taking out the dust. Good news is that when you spray or brush over the sanded area, it will still look nice and smooth when dry. Speaking of drying...
This is the bravery part I mentioned and is true, not BS. I've sprayed the stuff on and been able to sand it within 5-10 minutes, respray and still have a smooth finish with no blemishes. I spray rather dry, so if you spray wet you will not be able to do this. In any case, it takes practice and I'd recommend this be tried only by the brave
or crazy!
Seriously tho, it can be done.
The key thing to remember is this: build up several layers of the stuff before sanding, if you choose to do this at all. Future may "look" thick when it's applied to the model, (especially if brushed) but it's really a rather thin coating. Not as thin as some model paints, but you'll sand thru one coat of the stuff in a flash. Build it up some, then sand.
Fade to Black...