Any greaseable-bearing pedal is going to exhibit drag from the grease; it's just the nature of the beast. The only way around this is sealed-bearing pedals. As you suspect, the spin, or lack thereof, is determined by the volume of grease you pump in. If you want it to turn a bit more freely, less greasing but cleaning/repacking more often; less freely, pump 'er full and pump more in as the old leeches out.

Syncros includes grease ports in a couple models of their pedals (besides for lubrication of course) specifically for controlling rotation for certain stunts (no-footers, etc.) - - so that you'll know the pedals will stay in position when you take your feet off them.