I wait until my guy is in his rock cave hide, and then simply drag the mouse (with tongs, by the tail) back and forth across the opening, occasionally poking the head inside the hide if he doesn't hit it right away. Usually only takes one swipe across the door and it's gone. One thing is to make sure you're not making the rat look bigger than it is, sometimes they can get scared away if you're holding it legs-up so it looks a lot bigger than it actually is. I try to keep it down on the floor so he knows he can take it, sizewise.

I thaw the last way Jonah mentioned. I keep eat rat in a Ziploc, I take one out the night before, toss it into the fridge to thoroughly unthaw, and then keep changing the water to be really hot while it gets heated all the way through. Takes 30 mins or more with a bigger rat.

If you don't get it right the first time, don't get discouraged. Just keep trying!