Hmmm, I looked for it but can't find it straight away, but there is some information somewhere about weaning from a swing or car seat. From what I remember the recommendation was to use rolled up towels under the knees and around the baby to simulate being in that upright position, and gradually decrease the size of the towels till baby was able to sleep in the crib again. If he is a motion addict - needs the swing going, you might try gradually decreasing the rate of the swing, and then work on getting him into the crib with towels. If he is a car seat sleeper, you can start by putting the car seat in the crib and let him sleep in the car seat IN the crib, and gradually move him out of the seat into the crib with towels. You may want to try the props boards for better info, here is a link.
infohttps://babywhispererforums.com/index.php?board=28.0
Good luck with everything!!!!