For DS we just switched 1 bottle every second day for straight cows. Had no problems at all, he didnt know the difference. I just did it in his bottles otherwise too many transitions i think will cause problems in the process. I think it wasnt until he was about 16 months or so that i changed him over to sippy cups for his milk.. just bought some and started calling them his bottle. They are Disney Pooh Bear ones with yellow and green lids (2 in a pack).. they have a pointed spout. He had no problems with that either.

But yeh, you might also find you wont need to give as many at 12 months. I think the average is 3 bottles as by then meals/snacks are most important for nourishment. DS just started one day to not drink the middle of the day one so i just dropped that out. He now still has a sippy cup of milk when he wakes and one before bed(if he asks for it).

Best of luck!