For us what worked (on the breast, not a bottle) was to cut it down in tiny, tiny baby steps.
For example, my daughter would nurse to sleep every night. Eventually I said to her "let's fly up, up and away into bed after we nurse". She loved that, so we'd have a short nursing session and then the big swoop into bed. I made the nursing time a tiny bit shorter every week or so. Eventually we were down to one minute of nursing. I said one day that tomorrow night we would not nurse. Instead we'd just do the big swoop "up up and away". She was completely OK with it.
If she had a hard day/night at any time during this, we took a step backward and did not pressure her. I think we probably did this transition over a period of 6-8 weeks... can't remember exactly how long.
We also waited on this until she clearly understood language and could communicate well with us. Otherwise I saw no point in trying to make a change. She was about 2 years old when she was completely weaned, and she was definitely not ready before that (we'd tried a similar transition, she balked, so we stopped).
I think really the most important thing is to respect your little one's needs, whatever they are. If it's a security object, it will remain one until that need is filled or substituted by something else, or if the need itself goes away. Be careful what you take away, especially prematurely, because it could be substituted by a worse habit.
Like so many other short-lived phases, I always tried to realistically determine if it was actually a problem. If not, I tried not to focus on it. This is probably one that will either disappear with time, or can be helped with tiny adjustments over weeks.