either my daughter was ready or i was lucky.
haven't read all the responses yet....but....
we started talking about it for a couple weeks or so....about how her younger cousin and other babies in the world could use bottles....and that she had a bunch and could share hers with the babies that needed them. .......and then talked about the "bottle fairy". and that I heard she was going to be in our neighborhood soon......and then one day, how the "bottle fairy" called (could have the bottle fairy send a letter in the mail too) and wanted to know if she could leave her bottles on the front porch and she'd pick them up and deliver them to the babies that needed them. i told her a little bit about the bottle fairy and that I heard that she leaves special treats for the big girls and boys that share their bottles with the little babies.
so that night before bed we colored a bag and decorated it and put a note in for the fairy and then put all her bottles in the bag and put it on the front porch and turned on the light.
that night we went to bed and used a sippy. in the morning she woke up and on the porch the bottle fairy had left her some fun little presents .....including some special sippys and cups with fancy straws that she can use to go to bed.
it went really well. she asked for a bottle once or twice in the next couple weeks....but i reminded her that the bottle fairy came and got them for the babies that needed them....and she forgot about it...
good luck. as with everything - i'm a firm believer in if they are ready it will be easy....if they aren't ready...just let it go a little longer and try again....at some point they will be ready.....I don't know any 10 year old still using a bottle ;) ahhahaha