Michaelvk,
You assume correctly; Future Floor Polish is an acrylic, not a wax. It really doesn't need to be thinned in order to push it through an airbrush but, if desired, you can thin it with plain 'ole water. I wouldn't recommend alcohol, it does funky things when mixed with Future.
I've heard Johnson's Clear referred to as the European equiv to Future, but I'm not sure if it's the same exact stuff. All the European modeling rags I've read usually have some reference to Johnson's, so it must work well, in any case. And your questions aren't daft!
Toad,
You'll find that Future is VERY forgiving and quite flexible. It's a dream to work with; it's self-leveling so if brushed on, it won't show brush marks. (Unless you keep working it as it starts to set!)
It also sands very well. I don't necessarily recommend doing this, but I've been able to spray the stuff on and sand it within 5-10 minutes and then respray. That was kind of an emergency measure due to the circumstances, but it worked without a hitch. Also, I spray rather dry. Many folks spray wet and this may not work if you spray it on thick.
How's the Stuka coming?
Fade to Black...