A followup to my earlier post.
The idea is actually quite common, but still, I believe many don't know.
Peter Gregory has nicely described the method.
And here is a proof.
I just like to add a couple of pointers from what I've observed.
1. Don't be so conscious that you are learning to ride. Just have fun gliding the walking machine.
2. Objective is NOT to move in a straight line (thus roads and paths are not suitable), or how to make turns. Just have more fun by moving faster and with legs above grounds for longer periods.
3. Soon, you will find the above not challenging as the speed achieved by pushing is slow, and legs get tired from holding them up for too long. i.e. you have learned the balancing part.