When I was planning my HB, I looked at private banking (not donations), but their process worked fine for homebirths. Basically they send a package with all the equipment that is needed, and directions. They assume medical staff is doing it but there's nothing about the process that requires medical staff or anything like that.
We did not cut the cord until after it stopped pulsating. And then got absolutely no blood from it. Since it was a private banking company, we had paid a deposit, but they refunded all of it minus a small and reasonable fee.
Anecdotally (just reading other's experiences), if you wait until the cord stops pulsating, you are unlikely to get enough to donate. But sometimes you do. The fact that most often there's not enough tells you something about the natural process - that is, most babies in this country are deprived of their birthright (their blood) on a day that they really need it (being born requiring a lot of energy and healing and adjustment). We would never draw that much blood from a newborn, but somehow it's seen as ok to deprive the newborn of that blood from his or her cord.
Personally, I think that if someone is very interested in donating or banking, they should attempt it only after the cord stops pulsating, and not count on it working. If they get enough, great. If not, then the blood is already where it is most needed.