Painting a Zuzzy mat for Ogre Miniatures play

I recently obtained a large (4' x 6') Zuzzy terrain mat, and have been painting it for some time now. This picture is what the mat looked like before I started painting it:

I brushed a wash of earth brown over the whole mat, next time I'll spray it with my airbrush...

Next I airbrushed a thin black wash over the whole mat, concentrating in the darker areas ...

Now for the fun part, I picked several colors to correspond to certain types of terrain on the mat, and painted all of them. It ended up looking very paint by numbers...

Now I airbrushed more light washes of black over the areas I wanted to be darker:

After letting the mat dry a few days, I started drybrushing the various areas to bring out the details, this is the final result:

Finally, a closeup of one of the volcanic-looking crater areas, I also picked out a few of the individual rocks in different colors to break things up a bit:

I love this mat! I can't wait to start playing games on it.