Curious at what age to nap train and to find out any helpful hints.

DS1 I never napped trained and he napped usually in our bed and I almost always laid down with him until he stopped napping earlier this year at 5.

I can’t do this again. DS2 is going to be 5 months this weekend. He currently naps in the RNP (which has to stop), his car seat or being held. Right now I nurse or rock to sleep for naps and he will transfer to his RNP but not the crib. Two naps usually line up with drop off/pick up of big brother so I leave him to sleep in his car seat when we get home.

His first nap is always at home. Will it even work to nap train if I can only for sure do the one nap in his crib?