well...there used to be a can tutorial...they arent too accurate but what I did for my old boba helmet...
I went to walmart and got the large Aerosol can Airbrush thing. With the topper that goes on the propellent can...i think used dixie cups and sprayed the different greens in there till i got a mix of colors that looked spot on, then shot it on the helmet...the colors turned out real good and were real close, for the damage, i would draw out your damage w/ a pencil first, then get some acrylics, or once again, spray in a dixie cup, and dip your brushes in and go for it