The following is a what I found on usage..it's rather dark footage: http://youtu.be/KxlTms4jGKE
It appears you drag or pull the equipment toward you & lift the front off the floor to move forward for the next pass. The difficulty in going forward may be due to the direction the brush is rotating. Usually with a carpet machine where the pick-up or suction is located will indicate the direction of travel...as you want to remove the solution. You might also want to follow-through with your pass at the end (without spraying solution). Following-through will prevent you from leaving small wet spots the vacuum didn't reach at the end when your finger was still on the trigger.
I personally prefer a carpet wand even though it doesn't have a brush to aggitate the fibers. I can go forward/back a couple times over the same spot with my final pass removing remaining solution without spraying more solution.