On a high bar or on a floor bar.
The trick is to simply practice them. If it's a floor bar, kick into them and try 3-4 times as a side station before going back to the bars.
If this is not working at all, work on a handstand trainer or set up a floor bar on tumble trak or a low bar on mini tramp and bounce to the HS.
You can also set up a floor bar against a wall and practice tap-bouncing your toes off the wall ( or a soft wedge ) and feeling the free HS before coming back to the wall. Stomach facing wall.
