How do nurses do painless sugar level checks?

I had a nurse that checked my sugar level before a surgery when I informed the hospital staff that I was hypoglycemic.She pricked my finger,and I kept waiting for the usual pain that came with the procedure. It never came.I thanked her for her skill,of course,but I was left wondering..why do some nurses leave my finger sore for several minutes,and others don't?Is there a skill to a finger prick that some just never pick up?