Weaning 6mth old off dummy to aid future sleep training?

[Victoria2002]

DS4.5m has had a dummy since 3weeks old when I started using one (out of desperation)! Although it definitely comforts him, he's never been any good at keeping it in his mouth eg; if he's vertical it drops out, and when he falls asleep it drops out and he wakes looking for it after 30mins. For this reason I tried not to use it at night and have been giving the poor child mixed messages by using it in the day for car journeys (he hates his car seat) and naps, but not using it at night.
At night he wakes every two hours, and feeds for a few minutes (he can get a full feed in this time), then nods off again. I'm pretty sure this is just habit/comfort feeding and would like to try to sleep train him at 6 months. I suspect I need to give up the dummy in the day to sleep train him successfully. Does anyone have experience of this? I would ideally not do both at the same time, but wean him off the dummy (how)? then try sleep-training to see if he can learn to sleep for longer stretches.
He tries sometimes to suck his fingers but he puts them so far into his throat he gags and even vomits sometimes.
Should say also I hate the dummy for lots of other reasons like wonky teeth/speech/hygiene etc
Any experience please?

Hi, have no solution on the sleep training but am watching with interest my 22 week old is dreadful at naps in the cot. But just wanted to say about the dummy my DS1 now 4 had one for sleep only until 18 and his speech and teeth were not affected. He was only ever allowed it when he was having a nap or poorly and had to sit still with it, it really helped especially when he was poorly. He was very active and never wanted to sit still so it worked in our favour. But I do know of friends who just went cold turkey at 6mo and it took a few days but LO accepted or learnt not to have it. Hope the training goes well I'm am dreading it find it easier to let DS2 sleep on me or on the move.

Jezza I also posted in AIBU where there are more replies.