Just go suuuuuuper small, and really just get used to the texture of the feature. Once your on, DO NOT FIGHT WITH YOUR MISTAKES!
If you're going to slide off the feature prematurely, then let it happen. If you're some how slowly spinning on the feature, let it happen. The less you fight, the better it treats you.
Just stay the same position all the way through. Work with 5050's first. then boardslides. just keep your knees bent, and try to be as sturdy as a rock. Once you get your slide through a few times, then it becomes exponentially easier to progress from there.
Recommendation...wide stance, it almost FORCES you to keep in that hunkered down position.