Brake cleaner.... ?
To clean my calipers I take them off the forks, out of the way of the wheel and disks, and give them a good coat with some degreaser like Simoniz to get rid of the crap. Use a toothbrush to work the dirt out, and repeat until they're clean. Then I use brake cleaner to get rid of any deposits, again working with the toothbrush, until they come up spotless.