Some people say push harder to go faster, some people say pedal in circles. I say until you can fully un-weight the trailing leg you're doing more work than is necessary. At the bare minimum you should have no back pressure, i.e., the trailing leg should not rest on the way back up.

Ideally you'll be pushing hard on the down stroke and pulling up as hard as possible on the return. Your push will always supply more force as your (massive) Guads are the larger/stornger muscle.

Lots here about pedalling circles. You'll be pleased to know hard core fixie riders find using powercranks the easiest, i.e., unweighting the rear leg. However, even ultradistance fixie riders feel there is a benefit in using them as it adds that little bit extra to the down stroke and completely removes any un-necessary back pressure.

Also, until most cyclists have used powercranks they don't realise how un-coordinated their pedal stroke is, i.e., perfect timing of push/pull so there's no excess work. Single leg drills just don't have the same effect.