Slowly working my way through a BUNCH of vehicles and finally decided to bite the bullet and do the camo. Still a lot of work to go, but this is a huge jump in terms of looking done. Masking tape took 8x longer to put on than actually painting did. As someone new to an airbrush, I must say that it's definitely faster and smoother than using a brush, but I really need to improve my aim. There's some nasty overspray in various places which is going to have to be touched up by hand, but I'm generally very happy with this.
I know of some liquid masking products specifically for mini painting, and I've seen others also use silly putty (or similar). As far as I know they both work well, the main reason I went with masking tape was because I wanted nice straight lines and sharp angles.