ive always used the same pin to draw and inject, with no infection. as far as the pain, deal with it, my abs hurt worse after a workout then a little pinprick does....my motto...get big, get big, get big....:stick: just watchout when you pull the pin out, put a napkin or piece of toilet paper in the same hand your pulling out with, pull out and let the pin hit the floor, while immediately puttin the napkin over the injection site...dont let the blood spray everywhere, unless you like that kinda thing