Its easiest to skid if your feet are at 2 and 8 o clock. Pull up with the foot at 2 and push down with the foot at 8.

Experiment with which foot is at the front but after a while you'll be able to switch and skid in other positions.

Nuts on the stem makes it easier to unweight the rear wheel but you can also just kinda hop the back wheel to skid easier if you want to do seated skids.

Pick up some speed and commit to it or no amount of good advice will help you!