This might work good for small airframes, but for models of that size these lines are much too crisp.....they need more fuzzyness on the edges. I simply use a very fine airbrush and spray it on. Works on 1/72nd scale, works on 1/7. Just be careful to always spray towards the color you are spraying (i.e. if you paint a circle with fuzzy edges, always spray towards the center of the circle, not from inside out).
The amount of paint coming out of these very fine brushes is limited, so you'll never notice that fine mist all over your airframe like you do with bigger guns. Works great, and doesnt leave that hard-edge look.....that really doesnt look just right...