I read the threads about learning how to spin (and not mash) and the exercise where one leg practices the spinning motion is not going well....at all.

I can barely get my legs to spin equally throughout the stroke! I can only do it with an extremely low cadence..and it's impossible in low gears. I can spin with both legs in higher gears on the trainer but not in low gears--I just keep mashing.

The other leg rides along during the one-legged exercise, correct?

On what part of the pedal stroke should I be focusing?

Any pointers that can help me with my frustration would be very much appreciated!