Hi K.,
I have great admiration and respect for you for taking on two teenagers, on top of your 2 girls. Good for you! Now, about the pull-ups. I don't know if it will work for you, but it did the trick for me. It was taking forever to get that anticipated dry pull-up in the mornings, so we made a cute little chart (with a pic of her on the big girl potty) and every time she used the potty on her own-she'd get a star on the chart. If she woke up with a completely dry pull-up, she got a special glittery star. Sounds so simple put it did the trick. It took less than one week for her to discard those bulky ol' things and get in to her much coveted "sponge bob" panties. To help fuel her incentive, let her shop with you to pick out all the stuff you'll use on her chart. I still have my daughter's chart as a memento of that time in her life and she is 17 now! Wouldn't she just love it if I brought it out to share with future boyfriends?! Ha-ha-ha!
Best of luck to you and again, thank you for stepping up to the plate with the teenagers. You should be very proud of yourself for making the right decision -- not the EASY decision--but the right one. You've already changed two lives and now you're working on two more. I wish we could clone you!
V.