Thanks, Chris. I'd recently learned about Texture Guide but didn't think of trying that at all. I'll give it a go.
Oh, and btw, how much have you used Houdini, out of curiosity? I really like it, though I have a long way to go. I eventually want to be able to create semi-complex models and try changing something in the early stages of the model, and then re-cooking. I've heard it's pretty amazing.