I run a "toilet paper" type oil/water separator... basically a cartridge style that holds a filter about the size of a roll of toilet paper. If I'm going to need really dry air - 1/2% of the time - I use a desiccant hose in line ahead of my spray equipment.
http://www.amazon.com/DeVilbiss-1305.../dp/B000UZPPKA
This is plumbed permanently in line......
http://www.amazon.com/gp/product/B00...ilpage_o02_s00
Otherwise I just run a deadhead line with a valve that extends beyond the regulators... open that once in awhile and blow the little bit of condensation out (in addition to daily opening the condensate valve on the bottom of the compressor tank).