Look at some paint blending tutorials for photoshop, it's quite easy in the theory but takes a good while to learn(practice practice pratice!). Basically, paint a color, and with color picker and Opacity Pressure enabled in the tablet, you start painting and picking up the midtones resulting from the opacity changes to…
This is way over complicating things, and the advice already given here is much better in the short term, but learning texturing is very similar to learning digital painting. Try flicking through the tutorials here, and you'll find a lot that will teach you how to use the painting and editing tools in photoshop better.…