I found some small "natural" sponges in the Wal-Mart craft section.  I didn't cut them up as others have.  I started with a basecoat of medium/light brown (actually Nutmeg).  Then I sprayed on areas of light green, green and lighter tan.  Using those colors I defined the edges of the painted areas with the sponges.  You want to leave some areas where the color "fades" from one color to the other (from brown to tan or light green to green).  That, from my eye, is a big element in mulitcam.  Not just blotches like woodland but areas where the colors blend.  I atually wish I had more areas like this in mine but you can't add those after the fact.

I then blotched on these same areas with the same colors to break up me larger areas.   Finally I blotched on the dark brown in a small amount and then an off white in an even smaller amount.  I actually did less "blotching" and more "painting" with the dark brown and white.

The friggen white paint was lousy and went on thick and clumpy

Overall a 2 hour project - pretty easy.