I use Paterson proofers, enlarger as light source. As I use colour head (with variable contrast papers), I use mixing chamber, lens, and negative carrier for 35mm or for 6x7 (depend what was mounted on enlarger from last printing session). I raise enlarger's head just enough to cover all area of proofer. Focus lens as for normal printing, set aperture on f11, remove all fiters (set all filter dials to 0), and for me and these settings, 10 seconds of exposing is what I use.
When use condenser head, I do all the same, that is, leave condenser, lens, negative carrier from last printing session and make contact proof at procedure like above.