Thanks Arsheesh! I think the blurry effect has two causes. First, I did an erosion pass to get my rivers - incise flow didn't work properly for me - and I think that may have given me a softer result. Second, I painted the masks for my different color layers with a soft brush. Next time I'd use something with some texture. Definitely room for improvement, but at this point I'm happy to have something that isn't a complete eyesore.