I have found that if i want my doctors to progress, works with the builders as well, to acually place them on one of the herbs, and then exit the game b4 they are done, usually what i do after im done playing, is pause it, move everyone to where their supposed to be, and then unpause and exit right away, when i get back, their skills are twice as when i left, and some more.
I left the game for about 2 hours once, and my trainie doc was a master, but on furthur checking, he liked herbs and bushes lol and i just got an esteam elder at 39, she was a master parent and then a master researcher, and then a master farmer, and the only reason she got it done so fast cause she likes work and turnips. lol lucky.