from the brickter, excellent step by step tutorial on how to create camo netting on custom minifig helmets, and they are really nicely done too! see here
Black tulle (netting)
A TLG piece to hold the helmet up
Step 1: Super Glue the complete outer-rim of the helmet.
Step 2: Pull down the black tulle (netting) down over the helmet, pull tight, and hold until the Super Glue dries.
Step 3: After the Super Glue dries, glue the outer-rim again over the tulle (netting).
Step 4: Cut the excess tulle (netting) as close as you can to the helmets outer-rim.
Follow these steps closely, and you’ll have a netted helmet! 😉