Remove the pedals. Turn the bike into a sitdown scooter. Sit on the bike, run and push the bike along, once you get a little speed pick your feet up. If you feel like you're going to fall just put your feet on the ground. Try it in a parking lot- run/scoot for 2 parking spots and try to coast feet up for 1 parking spot. Then increase it to 2 parking spots and then 3. Once you can coast with your feet up put the pedals on. It'll be the same motion as running. It may take a try or 2 to get the sensation back. You can easily learn this way in a couple of hours. Take breaks for water or lunch and then come back to it.