It was actually easier than I expected. I started with a base layer of brown, then used grass and vegetation from my yard as stencils.
I layed the vegetation (grass, pine needles, leaves) pretty thick, basically burying the stock so you can barely see it through the loose grass and pine. Then held the can far enough away as not to let the compressed air blow the vegetation away. Basically hold the can 3-4 ft above and spray down directly. Remove the vegetation and apply again for each colour. I did brown, then khaki, then finished up with OD green.