Tips on sleep training

So I’ve decided I want to sleep train my baby because what we’ve been doing just isn’t very functional for us anymore. She’s a baby that’s been rocked and nursed to sleep, and around 4 months old she started sleeping with us at night. She’s gotten used to having my boob at night, and is at the point where she almost always needs it in her mouth. We also never transitioned out of a swaddle(she uses the love to dream arms up swaddle), but I’ve just bought a weighted sleep sack to try to fix that. She’s 6 and a half months old and was previously napping good about 1-2 weeks ago, but recently she’s been having a harder time falling asleep, wakes up if put down, and hardly sleeps to or past 40 minutes. Any advice would be appreciated!