I've watch the videos and I think I've discovered the technique for a successful launch.....not that I've verified that it works or have ever attempted this, I have not.
But (pun intended), the problem appears to lie in the normal reaction of the human musculature to contract strongly when presented with sudden pain. This, as you can see demonstrated in the videos, would greatly diminish the chances of a successful release of the rocket shaft.
The procedure that may raise the chances of avoiding a skin graft might be in clenching up tight BEFORE the stem of the rocket is put in place, and it should be put in place lightly even then.
I would be grateful if some of you who are more adventurous than I would give my theory a test. Looking forward to hearing how it works out. Video not necessary.