What's at least as important as what grease to use is how well you clean them, inspect them, and if you find any dings that might hang them up smooth them out with emory cloth and/or a fine file. They gotta be smooth to start with or the grease won't make much difference.
I agree 100% also put a little brake fluid on the little o ring near the tip. And when I do my brakes I take a toothbrush and clean the pistons with brake cleaner then push them in. Each to there own but I believe the pistons must be cleaned as well.