hey i had this problem when my dd was distressed over her jabs. I had always been strong and she had only had her dummy in the day before.
( naps, or in car etc)
she kept waking up everytime it fell out or every time she entered a light rem.
i was adviced to put it in and wait, you can see them sucking it as the sucks become less and less and have breaks in between gently but firmly and quickly whip it out.
it is very cute as their mouths still suck!!!
you do have to get the timing right, sleepy enough not to wake up but not in a deep enough sleep that they dont recognise it has gone.
it works as the last little bit they fall asleep without it so therefore when they light rem they will just do the sucking motion.
it took a couple of attempts on the first night to get the timing right, and over a couple of nights for her to not wake for it again.
she doesnt have her dummy hardly at all now.
( only when in a car seat or first put in a pushchair, wonder if it might be mild travel sickness coming )
it is a god send when they master this art!
hope that helps.