HI Rich!
Believe it or not, I've used this technique with good results. Haven't done it for a while but it is a valid method. I used it a lot when working on a plane with a natural metal finish. I'd cut some patches of newspaper, block off a panel which needed a different shade of NMF and use the airbrush to apply the different shade. It's pretty much as easy as it sounds. I'd get a bowl of water, dip the newsprint in, then lay it on the plane. Before spraying I'd dab away the water because you don't need to have the paper sopping wet. If the paper is nicely damp (and not sopping wet) then it actually dries sort of quickly so you have to work with a little (not a lot though) of speed. You don't have to rush through it, just use common sense and don't leave the paper on for half an hour while you do something else. The paper won't absorb or "wick" the water away from the area which you are trying to paint. Just think of it as being the same as using tape only the "tape" is slightly wet. You shouldn't get any newsprint on the model but if you notice any then a wet paper towel will take care of it. It's actually a great technique! Hope this helps.
Eric
PS. Now that I think about it I used this method on my B-36 when I had large areas to mask off and didn't want to use tape which could have marred the metalic paint.