Well,
@KiwiMoose I can bore you to death with my vast range of experiences and failed experiments on this one.
You definitely can cure CP shave soaps in mugs, no problem at all. I've done it and there's an Austrian girl who makes some great soaps poured direct into a mug. If you want, I'll look for her link.
I don't hold much with all the concern about breaking ceramic mugs, I draw the line with glass though.
It depends a lot on your technique: I use some kind of a container to hold the soap (enamel mug, deep ceramic dishes, which are dirt cheap in Spain, metal tin) and there I load the brush, then the hard work goes into another mug where I make the lather.
The issue with the container is finding the balance between depth and width. Too deep and narrow, you can't ram your brush in there, too shallow and too wide and the soap pours over the side like a nasty attack of rabies. I've used an enamel mug that looks great for throwing into the dirt before shooting Lee Van Cleef between the eyes, but the depth, the depth. I've also used some deep ceramic dishes, rough and tough, used in Spanish kitchens since the emperor Hadrian and they're brilliant because they have a slightly rough finish under the glaze that's fantastic for coaxing out the lather (another point to consider: mug too smooth, lather not so abundant). Their only drawback is being too shallow.
I'm half dead from gym frenzy and work right now, so I'm not making much sense. Let me get some sleep and I'll happily write more on the subject. It's where I'm going right now in soapmaking, so it's very interesting to me.