For info on using Future, check out "The Complete Future" and the "Future FAQ" in the Techniques section of the forum. It will answer virtually any question you have about using Future, and some questions that you didn't know you had
For brush painting, look under "Techniques" in the "Browse By Subject" in the panel to the left (not the "Techniques" section of the forum). There is an article in there about brush painting, but I don't remember the name of it offhand. It's pretty good and will help you a lot.
For airbrushing, here is the secret. It's simple really, and all of the good airbrushers have figured it out. All the rest of us are still trying to. The secret is: PRACTICE! Nothing will take it's place, there are no shortcuts, there's no way to suddenly make yourself into an airbrush expert. It takes practice, pure and simple, and lots of it. One of these days if I keep working at it I might even raise myself up to "Decent" status!