I just went through my own self-learning indoctrination on camoflage myself. I've done the soft edge style by either spraying very close (and lightly) to get the basic outline (border) of the pattern and then fill in the interior of the pattern with more flow and more distance from the model. I use a double action Iwata HP-CS, so I can control the amount of paint that is being dispersed.
For crisper edges, such as a 'splinter' scheme on WW2 German aircraft, I have used frisket paper, masking tape, and 'Post-It' notes. The frisket would almost always pull up the previous color coat. The masking tape (Tamiya's, don't use regular masking tape, nor even the blue type) worked well on contours and canopies, but I backed it up with Post-It notes to completely cover the spray area. If you want the soft edge, but straight line look, Post-It notes work great, as they really don't want to adhere tightly to the surface.
Best way I REALLY learned to spray irregular patterns and develop control was to use the remaining paint in the cup (say, after spraying an overall base coat) and spray it on just about anything at hand to practice on, like another Post-It, an old FedEx envelope, the cat, whatever is at hand. I probably put more paint on my test scraps (ask the cat) than I do on my models, but the practice is worth it to get it right when spraying the model.
Best advice I can give is to be willing waste a bit of paint for the practice part. It's a lot easier to do that than to commit to yourself to something you've spent so many hours of assembly on, and then still have to sand it off and repaint anyway (believe me, I KNOW that part.)
Also, if you prep your models with a sandable primer you can kind of experiment that way on the actual model. I think it's kinda funny that when I casually spray primer over a filled-in joint, the result is a better camo pattern than I would have achieved if I'd done it deliberately!
Anyway, don't be intimidated by the whole thing. Try a few things as a test, breathe, get yourself relaxed and go for it..