This is how I do ballistic hamstring stretches nowadays, it was inspired by the Phil Lancaster post and a little experimentation:
- Sit down, pull your right knee to the chest and lay your torso onto it. Your knee will be at around 90 degree or less.
- Let the left leg take care of itself, it will likely exorotate to the side, it is okay.
- Hold your right foot (if you can't reach your foot in this position use a towel) with boths hands and do the following:
- Using your calve pull yourself into a stretch. These are very slight gently and rhythmic pulling or pulsing actions. Do this for 20--25 reps with 2--3 reps/sec.
- Straighten your right leg ~10cm
- Repeat the gently pulses.
- Repeat this two or three times, always straightening the leg a couple of additional cm
- After the last set place your hands on the foot (use a ball if you cannot reach it) and try to push it away while simultanously pulling your foot with the shin muscles in direction or your body. Do the latter with a similar frequency as the first pulses. So 20--25 gently pulses while you push against your foot. As the direction of the pulses is reversed, you are no longer pulling yourself into a gentle stretch but out of it, but you will still gain ROM during this last cycle
- Now switch legs and repeat the whole procedure with the left leg.
- When you are done repeat the whole process with both legs at the same time.
This works best when you place a pillow under the foot of the leg your are 'stretching' so it's a little elevated. If you like you can bend over both legs before switching to the left side, the difference in perceived tension will likely be dramatic.