I haven't done it yet, but I am getting ready to try. I looked at some videos on youtube. One guy masked a camera, sprayed it with glue, and then covered it with bark and other material he had pulverized.
My plan is different. I took the bark off a dead tree. The bark is one piece about 18 inches long and several inches wide. It came from where a limb had attached to the tree so it is curved. I am going to hot glue the bark to a security case. I know trees have different bark but if I can find a tree with a similar bark, the setup should blend in.
I am also going to make 3d camo for a python lock. Someone had thrown away an artificial Christmas tree which I picked up. I cut off the branches which are flexible wire with artificial needles attached. I am going to paint a camo pattern on the branches and then wrap them around the python cable. That way I will be able to slide the cable into the lock.