[Blarg]

Kind of and kind of not. Some toughening of the skin and of the tissues underneath is going to happen naturally, and you'll want that, because when you move on to harder grippers the pressures get pretty intense. But if you get big callouses and they are untrimmed, they will tear.

So most of the real dedicated people get corn-huskers lotion or some other moisturizer and file away/snip away callouses when they get too big.

They definitely are a b*tch on the hands. They make them with those deep cut-outs so they won't slip, but that makes them harder to practice with. Unfortunately all the best quality grippers do that. The knurling itself isn't too bad, but it's the cut-out parts that really tear into you.

You can use the trainer for a while, to build up general toughness in the skin and to prepare your tendons and ligaments for harder things. You can exercise your hands to an incredible extent, and they heal extraordinarily quickly. You can also help that healing along very dramatically with contrast baths. So you can practically work your hands as hard as you like, within reason. But it's best to start out with laying a foundation of tendon and ligament strength and tissue toughness, so you'll get plenty of use out of your trainer for a while. If you ever feel you've overdone it, contrast baths will set you straight again.

Remember you don't have to just do closes. You can also do negatives and holds. That can put less wear on your hands sometimes too. Close with two hands, then hold with one, or slowly let it open with one.