Ah ok - yeah I understand about the nice metal finish - 95% of the guns i've painted have all been plastics and other wannabe metals. I've recently upgraded my old M16A3 to an all metal M16A4 and it's got a really nice metal matte finish that im having doubts about painting. Thing is it's a huge black gun...
Most painting techniques are usually 'whatever works' best, but for the most part I always try to do the following when painting;
1. Go from light to dark. Start off with applying a lot of khaki krylon (cheapest and best matte base) to wide sections of the gun, vertically (gun is held horizontally so pattern should go with the trees, grass, etc). Best thing to do is to paint the gun hanging sideways and stroke side to side. Don't cover the entire gun with base, just make 2 or 3 'columns'.
2. Apply second color, usually darker one - like OD or Brown depending on what terrain you are painting for. Experience with the Khrylon camo tones, especially the brown, is to use a 'misting' of khaki khrylon before putting down the brown. It seems the brown has a tendancy to go on really dark and gloss up on plastic/flat surfaces even tho it's a matte. Putting a really light misting of khaki fixes that problem.
Even if you just want to use khrylon OD and brown on your gun - use the khaki as a base. It brings out the color and texture with much better results.
Stenciling is really what you find out in your backyard. There are a lot of interesting patterns but just consider getting a lot of samples. Especially if they are leaves and not evergreen. The paint drys slower on the leaves and it blobs making your pattern look teh ghey.
Stenciling is effective if it's done at the edges of the 'color columns'. Use the opposite color paint one or two passes, then the same color as a shadowing technique to stenciling. A few tries and you'll get what I mean.
Another technique is tiger striping. Get a bunch of different sized twigs and sticks - the longer the better, and bunch them up into your hand. This works effectively when using a dark color, like brown or black - and it really breaks up the pattern.
Basically lay the bunch of twigs out in your hand so that they make a flat fan pattern, then press them up against a large section of the gun. Do one or two quick passes until you get the desired effect. C'est cool ca!
Some of my work;
If anyone else has something I painted - feel free to post it up.