C.B.
Try offering him a sippy cup (a really fun one with bright colors or a cartoon character he likes) and call it a "big boy cup" at one of his usual bottle times. If that goes well, expand to another meal, and so on. Probably this will get him easily to just bedtime and/or naptime comfort bottles which you can phase out in a similar way. Take it slow with lots of positive reinforcement when he reaches a milestone, no negative if he balks for a while.
Good luck!