Oh dear, yes, sometimes you just have to bite the bullet and work with the reduce brush (y) to piece brush down geometry, which often takes many time stroking over the dense polygon regions. This is actually the kind of stuff that should be shown in a video, too. As h2o already said, use that and smooth, but sometimes you might have to also inflate to show certain polygons that are bunched up on top of each other.
Anyway, there's no simple "delete" or cut off type of function in the nature of sculptris. I have to admit, though, it happens to me, too, that I would want to have that feature!