If you're trying to get the hang of your presses -- plural -- in one session, you may be asking too much. One size does not fit all. Pick one, and get used to working with that one, then move on to another one. If you keep switching back and forth, your eye won't get used to judging the right amount of glass and the right shape for a particular press.
I made my "template" beads out of polymer clay so I could bake them and they'd keep their shape. I have them on my work table marked with the size of the press they're for, so I can pick them up and hold them next to my mandrel to see if I have the right amount of glass. Sit down with your presses and a glob of polymer and play with the presses until you get a good press. Once you do, you know you have the right quantity. Then keep shaping that ball of clay around a hunk of mandrel until you can press it and have it come out perfectly pressed. Now -- remember what it looked like before you pressed it, re-form it back to that shape, and bake it so it stays that way forever. Presto -- template!
My bead release cracks a lot of the time. When you're working, try to be super-careful to keep your flame away from the mandrel, so you're not heating and cooling the bead release. Heating the bead release will cause cracking.
Try making sure that the core of your bead is good and hot before you press. Yee's comment that "you're pressing too hard" is a new idea to me, but it got me to thinking. If you're pressing hard, it's because you're meeting resistance, which means that at least some of your glass is stiff, that is, cold (probably). The surface of your glass might be nice and soft, but maybe the inside isn't chewy (the reverse Tootsie Pop effect). I make big beads, so by the time I get around to squashing time, the center has cooled off. Even though I try to let the heat penetrate to the center, maybe I'm not doing it enough, so that's why I'm breaking bead release. Hmmm. I'll give a little more time to letting my heat penetrate, and see if it saves my bead release.
On the other hand, maybe you just don't know your own strength.
