I've been on motorcycles since 1973. A year and a half ago I saw an ad for an underpriced Ural an hour away from my house. I'd never even sat in a sidecar before. I rode over on my FJR and the owner gave me a ride. I said "Done deal" and he said "Your turn". We went to a school parking lot and I rode with him in the sidecar. I rode him back to his house, paid him and left the FJR at his house to pick up later that night. I've since ridden our newer Ural across the country without issue. I'm not saying that training isn't worth it, just that it really isn't such a big deal. I describe it as riding a very lopsided snowmobile more than a motorcycle. I'll never be a 3 wheel only guy, but a absolutely love my Ural Gear Up.
edit- no doubt it is good to practice in empty parking lots. I did when I first bought the 1997 Ural.