I get best results with cables. I use one of those freemotion machines:
http://www.dazadi.com/images/p200/freemotion_VFMCS4007.jpg
I stand in front, use both handles at the same time. since the cable is a bit in front of me, the force vector is just at the right angle if I keep the pinky-up, or at least if I hold my hands leveled.
If the machine is a line of people waiting, I use dumbells… but to get any effect at the start position, where the weight creates no load on the muscle, you need to really accelerate the weight, then at 45 degrees, switch to squeeze motion.