speaking as someone who has never understood the concept of backside tailslides, but as someone who has previously had the nollie version on lock, the other day I spent an hour or so figuring out how to get into them on curbs. I think this is good, if only for getting used to the motion. If you concentrate on it too much, then you're going to find it hard when you try and roll up to anything higher with any speed.
That said go skate a curb and scoop the shit out of that back foot, it's all in the shoulders, and I'd suggest a slight angle at first....
Feel free to ignore all this though, as I've only just worked out the motion to get my tail onto a curb and the aforementiond nollie version on blocks has long since left the building anyway... Just know sliding a backtail to regs to fakie from regular or from nollie feels awesome. And that's what counts. Now if only I could do back 5's on anything higher than a curb, and then figure out how the hell you get into a Backsmith smooth enough to grind the shit out of it...
Fucking winter.