I cut to shape and also wrapped fishing net (the salt water kind, not the 'pick up the fish net' stuff) around my M24 then tied in strips of cadpat material, strips of OD mesh laundry bag, and some green jute strands (used for gardening):
And I purposely left the top of the barrel uncovered (bare netting) which helps break up the lines but also keeps crap from interferring with my sight picture.