Here's a short vid from my practice the other day. It's been about 20 years since I've done a proper drop back. Somewhere along the way I developed a fear of putting my hands over my head and dropping back. Instead had to put my hands by my sides, walk my fingers down my legs and at the last second, rotate my arms to meet the mat. I realized that it was seemingly more dangerous to do it the "incorrect" way because I was finding it hard to rotate my arms that fast and it could mess up my wrists and arms if I didn't get there in time. So, it was time to change. After a few practices with a spotter, I realized I had the physical strength to do it and the fear was just in my head. Moral of the story- face your fear and do it anyway.
To do a drop back- first and foremost make sure you are warmed up! Never go into this cold! Then, stand tall, rooting down into all four corners of both feet and lengthening up through the crown of the head. On an inhale, raise your arms up overhead, and engage the quads. Exhale and engage the abs as you drop back with control, keeping a microbend in the knees.