Lots of methods of camoing your rifle or shotgun.
1. Rattle can, available just about anywhere, you can go as simple or intricate as you want.
Base layer and some cedar fronds

Camo wrap, there is expensive wrap from your LGS about $12/roll or buy in bulk from an online source for about $1/roll.
You can use plain tan camo vet wrap also.
There is camo duct tape out there, I find the one from Gorilla doesn't shine, sticks well and doesn't leave much residue.

If you don't want to stick anything to a nice rifle, I'v made camo sleaves to kill the shine on my rifle.
Handy but pretty rifle.

I sewed up a camo sleeve and butt bage to break up the shine and protect the wood. Camo cloth, velcro and patience.
Getting the job done
I do use combinations also, painting the stock a dull color and tape on the barrel