Yeah using a hard edge brush would probably deal with the blurring problem, set it to about 80% opacity or something tho or the edges might come out Too hard.
I think you could also say the key to good traditional painting is good digital skills. I don't think it matters much where you start, it's all the same science but in slightly different applications. Can't hurt getting your feet wet with as many different medias as possible tho, gives you a new insight in what you're doing and will probably prove a good experience, so try it all. You're doing good so far, I like the alien character concept. So keep it up, an keep on updating. Peace.im told the key to good digi painting is good tradish painting skills