I bring two things in two the bathroom with me: a tall cup of ice water and a kettle of boiling water.

I add the boiling water to the "hot" water that comes out of the tap. I've done it enough times now to be able to guess-timate about how much to add of each to get the temperature just right.

The kettle keeps the water hot so when I need more for the second pass, I just add it to what is allready in the sink.

The ice water of course is for the cool down at the end. I live in Arizona. In the summer time our "cold" water is not cold at all!

This all sounds complicated. But it is all a part of the morning routine and so it is done pretty much automatically.

~Robert