I just painted my truck and I have areas of lots of orange peal and areas of lots of runs.  My friend used to work in an auto body shop and said to use a razor blade to carefully cut down the clear runs and then wet sand it with 1500 grit.

I have a paint nibbler coming supposedly (been on order for atleast a month) that's for sanding the runs and drips.  It's a little block with little file like teeth set just below the edges.  I'd assume it's rubber so it doesn't mar the paint, but you just lightly run it over the run and it'll sand it down close to flat, then sand like everybody else is saying.