I know a VERY fast way of becoming a master parent. It will only work if you have one or more villagers of the opposite gender, who are over 50. Keep placing the villager on a 50 year old plus, and do not wait for them to go inside. Simply keep putting him/her on the elderly villager, and eventually they will become a master. I used this twice to get JoaTs. It's a fast and effective way, but it IS cheating. Otherwise, if you have a young villager, just give them a bit of skill in parenting and let them do the rest. I only used the first option because my villager would have died of old age before I could master him.
By the way, it will take a while to get from adept to master. It may seem like the bar is stuck, but it is actually moving in very small portions.