on my camo jobs i like to use stencils i make, instead of tape. IMO, for the look i desire, it gives a softer edge. it's a technique i learned from a good friend of mine years ago who did lots of airbrush paintings on cars and motorcycles.
i make my stencils out of thick and stiff paper, that have irregular patterns i cut into the edges. i sometimes even use real plants as stencils.
i first lay a base coat, after properly prepping the stock for painting. this is critical in getting the paint to adhere properly. lesson i learned from being a painter in bodyshops, was prep work was the most critical part of paintjob on anything.
here are some of mine that i have done. i did the rocker panels of my truck as a test to see how durable it was under a bit more extreme conditions, like going through the woods and brush and using the carwash to clean it. it held up great and none was coming off, even after four years of abuse.