don't defrost under hot water. the heat will bring the surface temperature up enough to breed foodborne illness while the middle will still be frozen. Use cold water. Takes longer but it's safer.

If they're huge breasts, butterfly them so they cook faster and more evenly. If they're already cut into smaller pieces, it probably won't take an hour. Chicken breast cooks fairly fast and is easy to dry out because of the low fat content. Want to pull them out the second they reach temp (I think it's 165F internally). If you can't use temp, then learn to use touch. The firmness of the meat will tell you when it's done. You can look up how to do that. You can also cut a slit into it and look inside until you get an idea of how long it should take. Also make sure to let the meat rest when you get it out so it's more tender.