I like heucheras too. I have bought packs of mixed hybrid heuchera seeds and grown them, figuring that each plant would be different and maybe I'd get a good one that way. I've had a few good ones come up. Of course, if you are after some certain trait, such as dark leaves or red flowers or whatever, then I expect you might start by buying plants with those traits and crossing them. The actual process of emasculation and pollen transfer and such are not specific to heuchera.

Once, when I ordered a pack of heuchera seeds, I ordered a pack of tiarella seeds too, just for fun. I find that I like tiarellas too, and that the heucheras and tiarellas can be crossed to create hybrids.

Here is a link that might be useful: heuchera hybrid seeds