If this is with gimp have tried looking at layer modes? it's a nice way of applying textures to lower layers, mix that with layer masking and you can get some pretty nice results. Unsure if that helps. Not sure on your familiarity with the software but if you aren't familiar with masks check this tutorial out. Also I can throw a PDF together to show you some example of the layer modes so you can get a better idea how they work (haven't seen tutorial for the modes yet).