Hi mate, it's a lot simpler that you'll imagine, after a week of thinking about I finally grew a pair and sprayed my m4.
I kept it pretty simple, using Krylon paint, brown and khaki for the colours, and just a simple £3 scrim I got from ebay for the pattern.
I stuffed the hole for the magazine, the barrel end and taped up the glass in the scope and the end of the flash light and laser.
Any questions, I'll try help you out.
Dan