Hey juggler! Welcome to the forums. I'll try to help as best I can...
1. I've never used frisket film, but I would think that the thinner it is the better?? The current issue of Scale Auto has a good article on flames and they mention frisket film too, but don't say what thickness.
2. If you're going to paint on rubber/vinyl tires, you can't use enamel paints. They won't stick or dry. Try using a flat white acrylic from Tamiya or Gunze. That should work. I've also heard of people using White-Out correction fluid too...
3. Parafilm M is usually used for masking. It is very low-tack and is really stretchy. It will conform to almost any curve or surface with no problem. It might work OK for flames, but most of the things I've read suggest using frisket film.
If your Aztek is working well for you, then go with it! Don't get too concerned if others are having troubles with theirs. If you're happy with it and it's giving you the finish and versatility you need, then stay with it.
Again, welcome and enjoy the forums!!
Murray