Hi there! I realize this post is a few months old but I'll share a trick that I just learned, in case it's helpful to you or anyone else:
When you drag and drop your healer onto a sick villager, their skill level increases as soon as they
start healing. Don't let them finish the healing process just yet, keep dragging and dropping until they become a master. This should take up to 15 minutes depending on how much healing skill your healer already had before.
The same trick works with spiritualists and cursed villagers, it's much faster to train a master spiritualist this way than to have them pray at the pedestal for years and years
