Troutbum is right. At 75 years I find it easier to use one hand on the brake and one on the throttle rather than put my foot down. And it's so much easier than a motorcycle where you have to maintain the friction zone with the clutch and brake with your foot instead of just feathering the rear brake.
Stig, When you are in the parking lot, start by just doing larger turns rather than U-turns. As you become more adept, you will find that you will start making the turns sharper almost automatically as you, ironically, slightly increase the throttle. You will also find that your slow speed control increases in general as you master the "brake/throttle" dance. Almost as counterintuitive as countersteering, but it works. For some reason, left turns are easier than the right for me. And you're right, counter steering doesn't work at these speeds - you actually steer the bike and lean it slightly, accelerating a bit as you come out of the turn. Counter steering only works above 15mph or so.
And finally, you will be far less likely to run over your foot as you keep it on your scoot. Feet on the ground are good only for stopping - not for steering.