I painted my Marpat in a rather simple fashing doing straight lines horizontally and vertically on the uniform. Worked out rather nicely and from a distance it looks quite convincing. Close ups not so much
Personally I think the trick to camo is exaggerating the scale of the pattern to at least 3-4 times larger than it would be in real life. It give some resemblance of the original, while still being achievable. Plus a real size pattern would with most design just look like a smudge on the miniature. And go light on the colours. If I'd go back to my USMC I'd probably do at least the base brownish shade lighter as the minis are rather dark.
Also check out pictures of what the camo looks like on real troops when they are more than a few meters away. That's what you really want to achieve on your minis. It's all fine trying to copy a close up picture of the pattern, but really on someone 10 meters away the design will be very blurred out especially on some of the modern digital camos.
I also wrote a tutorial on how I painted them a few years back. Might be helpful. It can be found here:
http://engineered-gaming.blogspot.fi/2014/05/tutorial-usmc-in-woodland-marpat.htmlThe Vallejo Orange Ochre that I used as the base colour is a close match to the original, but on the miniature I recommend taking a bit lighter one, especially if you'll apply a wash later.