I have just went through the same thing with my now 14 m.o. Not that all children are the same, but this is what I did with almost NO troubles.
One night he just didn't have a bottle before bed. Instead, i gave him a transition cup. I used his same nUk bottle, but with the transition top (at walmart). He got that every night he went to bed from then on.
As for during the day.. we had to try about 20 different cups, no lie. Eventually he decided on the nUby ones (also at walmart, and the cheapest there). They're almost like a silicone nipple, but with a spout instead of a nipple. Still lots of softness around the spout for their lips. They leaked a bit after being used for awhile, but not too badly.
After about 2 weeks of those, we worked our way up for soft spouts, to semi-soft spouts, and now he is using toddler hard spout cups no problem.
I think it is easier for baby to go from different spouts than to only get a bottle at certain times of the day. It's less confusing and teaches them to drink from a spout no matter what they're drinking. My advice is to stop the bottles all together, if your baby will allow it, and try a trainer soft spout cup. Good luck!