I'm noticing that you're using photoshop, so you might be interested in the following thread: http://www.cartographersguild.com/sh...ter-Brush-work

It can take a bit of effort to get the technique down but once you do, it's worth the time. Basically, it allows you to overlap the brushes without the ones underneath showing through, which can help tighten up the mountains and hills so they don't look so spaced apart, yet don't look crowded either. Assuming you have a good selection of hills and mountains (the ones you're using include a great sampling for this) it's nearly as good as drawing them out by hand.