this video helped me the most with learning this trick
what worked the most for me was starting off trying to stall them, and getting the feel for slapping into the feeble.
keep your front foot in the centre of the board, a bit further back than for 5050s
approach them at a slightly tighter angle than for a bs5050, wind your shoulders and as you get into the grind shift your weight onto your back foot.
pull yourself out pretty much as soon as you get into the grind, and bring your shoulders the opposite direction