100% CERTAIN answer:

Talking to heathens will gain early devotion skill, once all heathens are converted any villager with some devotion skill might increase by dropping them next to the statue repeatedly and "honoring". Their likelihood to do so will depend on how much devotion skill they have.

If they do "nothing" next to the statue, leave them alone... they may decide to honor in a few minutes. I'm not sure if "praising" or "honoring the dead" helps but I always let them do it.

Breeding devoted individuals should produce a child with a tiny head start on devotion. As soon as they are born check devotion as the preferred skill.

Breeding two masters of all trades will increase the likelihood of a higher devotion start and give ALL skills a small head start. In some cases they can be born as an "apprentice devotee". As soon as they are born check devotion as the preferred skill.

In my experience if they are born with NO devotion skill they will never get any. You'll have to try with another child.

Have an elder (preferably the retired chief or another master of all skills) teach at the nursery school over and over. Any skills they are born with will increase during nursery school. KEEP the retired chief in your village by using the youth divine power over and over again.

Once the child is of age (14) drop it next to the statue repeatedly (this can take 50 times or more before they honor it). If they still simply will not, don't be discouraged. I have given up on several and come back to find they somehow maxed it while I was gone.

If none of the above has worked by the time they are 50 as long as they have a TINY bit on the devotion bar you can use the young again divine power. Each time they go through a childhood full of nursery school they will improve any skills they have and eventually become cooperative as they come of age. You can do this as many times as needed.