Okay, time to be the unpopular one around here!
Tamiya masking tape is great, but if you can't find it, try good old Scotch tape. It's thin, sticky, conforms well, etc. On top of all that, it's mega cheap too. Frisket film from Hobby Lobby works well if you're not just masking straight lines - or if you are masking straight lines. The frisket is a bit expensive though.
Painting the larger or smaller section first, depends on the paint job. Lighter colors first as a rule?
NOT!!! When working with lacquers, lots of people (me included) recommend painting the darker color first. I usually mix the 2 paints for 2-tones. I'll use a lacquer base color and enamel for the second color. Why? It's easy to clean up any boo-boos. Wanna see the best white paint job you've ever done? Lay down a smooth coat of black first! Yes, you heard that right. With enamel, it'd never work and never cover. With lacquer, it's downright awesome!
For more info, and some examples, check out the 2-tone painting and primer selection articles on my site:
http://modelcartech.com
Oh, btw, I ain't arguing with anybody, just telling what I've learned. What works for you, doesn't always work for me. What works for me may not be the rule for you. Basically, there's more than one way to skin a cat. If everyone did everything the same,, there would be no reason for this forum, magazines, more than one book on modelling, etc.
Experiment! And, above ALL, HAVE FUN!
Tim D.
http://modelcartech.com