I just tried a new technique on a model I built for my brother for XMas (it was
a Boeing KC-135 R. I know, I know, blasphemy!) and it worked pretty well. I
used some of the Parafilm M from Testors - that you can get for a whole lot
cheaper at a chemical supply store. I merely airbrushed the wheel color and
after it had dried, I stretched some of the film over one side of the wheel.
Then, with a sharp #11 blade, I cut the line between tire and wheel disk. I
removed everything except that which covered the wheel disk and repeated the
mask on the other side. Then I shot the tire color.
This worked pretty well for these particular wheels. I imagine that it would
work better in 1/48 or larger than 1/72. It also requires a fairly pronounced
demarcation between the wheel disk and tire.
<<I've deleted the rest of the questions 'cause I have nothing particularly good
to say regarding them!>>
Good luck and Happy Modeling! (Happy new year and all that stuff, too!)
John Roll