I'm NOT trying to be obnoxious, but there's a story about a motorist in New York who passes a fellow walking down the sidewalk. The motorist, trying to get directions, yells out, "How do I get to Carnegie Hall?". The pedestrian yells back, "Practice, practice, practice!"
Paragraph after paragraph on "how-to" could be written by both the novices and the experts on this forum, and it's all going to boil down to doing what works for you. For example, some will tell you to keep the brush moving. Depending on the technique, you don't want to do that. FSM has published many articles over the years on airbrushing. There are a boatload of professional airbrush magazine articles and books on processes. I would encourage you to read some of them. And after having read them, you are simply going to have to do what the rest of us have done: practice, practice, practice.
As far as Tamiya tapes go, I find that the 3M blue painter's tape that you can find at Lowe's and Home Depot works just as good. The stuff adheres well to the surface, but has a low tack, and is therefore easy to remove when done, and doesn't leave any adhesive residue upon removal (at least on armor models). The only downside is that the narrowest I've seen is about 1 to 1 1/2 inches. But then a sharp X-acto can cut it to the proper dimension.
Gip Winecoff