You'll be sad to know it's a lot harder to do. With front-surfing, you're used to seeing what's going on while controlling your boat. No such luck in back-surfing. If you want to get better at back-surfing, it will help to simply do more moves backward when you're just messing around in a rapid.
Practice catching eddies backward, do back-ferries, and so on.
The more you get used to controlling your boat backward, the easier it will be to back-surf. There's another hurdle to leap when you're trying to back-surf. A lot of boats today have a low-volume stern that just aches to sink underwater. The main thing you can do to prevent this is to keep your weight way forward think about putting your chest to your skirt. Watch you rear when back-surfing You can also carve.