What I have learned about blood draws is that it's all about training but, more so, experience. You learn more when you attach yourself to somebody who knows what they are doing, and listen and heed what the tips are they are giving you. It's called "follow them around and watch what they do!"....when you can. You cannot "arm hop" on me. Permission denied! Some people are just squeamish about what they are doing.
During a hospital stay, one young nursing student put a tourniquet on my arm that you could barely tell was there...that is just how loose it was. There is NO excuse for that. I did not allow her to stick me. Just understanding the mechanics is a start.....hello???