Zeno,
It depends on that the theme-of-the-day is.
Some days are 'hands' days. I practice pure hand techniques. Other days are 'leg' days, and kicks, kicks, and more kicks.
It it's a hands days, I simply do slow-mo techniques till I warm up some. Since hands days include footwork, some light streaching is done and I'm Gene Kelly (wish I could dance like he did.)
If it's a leg day, full streaching. Yes PNF streaching is the way I go now. I'll first warm up with some light hand techniques, then light foot techniques, then it's time to streach.
I do not use a streaching machine (at least store bought for that purpose) but instead use exercise bikes.
I place a leg on the bikes seat, say in front kick form, with the calf of the leg on the saddle, then lean into the kicking leg. Add PNF by pulling down hard like an axe kick. Then shift the rear leg out to force a larger angle, and PNF again.
Then bring the leg down and shake it some (or wiggle it.) Repeat with the other leg.
I then go back to the first leg, put it on the saddle, and then rotate to a side kick, making sure the knee is on the saddle to reduce stress on the knee. PNF again. Increase the angle again. PNF again. Swap legs and repeat.
I do the same above for a round house kick. Still with the knee on the saddle of the bike.
Then I hold onto a rail and do side kicks till I'm blue with one leg, then swap legs and repeat.
After that, I'm ready for the bags and a kick fiest!!
Deaf