I have seen the sponge technique as well but don't believe that it looks that great. I am starting to do this as a side job/for fun but don't mind sharing some secrets with you guys. Obviously preparation is key or else the paint won't stick/last long and if you need some tips with that feel free to PM me.
I start with a coyote tan base coat or something of the like. Spray the whole barrel with good coverage. While that dries grab some reeds (or in my case cut a section of broom off and use that) and tape them together at one end while fanning out the other end. You are going to spray through this to create the camo.
Next up is your dark brown followed by a light green and a dark olive. Obviously the dark colors are going to stand out more than the light so use your eye on how to build your layers. When spraying through your reeds don't spray across them or else you will get a lot of overspray at the ends. Just shoot straight through and take your time.
I am not sure about the rules on this forum and don't want to step on any toes or spam but if anyone doesn't feel comfortable doing it themselves I would gladly do it for you as it is kind of nerve wracking spraying your own gun.
I was able to field test the paint throughout the spring turkey season and I have yet to have any chips scratches or anything of the like, which can't be said about my friends dipped gun and I am a lot more abusive than he is.
Good luck and have fun!