I've found that routine is an excellent way to overcome many issues with children. For instance before you leave the house to go to the store EVERYONE uses the potty whether they think they have to or not. Then (mostly for the little one) as soon as we enter the store, if it's going to be a long shopping trip, EVERYONE uses the potty. Then (again mostly for the the little one) EVERYONE uses the potty just before we leave the store. This sounds excessive, but it's easy to lose track of time in situations like grocery shopping. I've found that I can be in the store for 2 hours easily. But if you make the trips to the potty a habit the brain begins to build dendrites that connect to the act of using the potty and the times it's supposed to occur. Just like using the potty right before going to bed and immediately after waking up. Or if a craft project is about to begin we use the potty right before(washing your hands before a project can be a plus anyway) and we go immediately after we finish the first project we were working on. Going outside can get a little tricky, that's when an alarm may come in handy. We use the potty first, then go outside, after about 2 hours we come in to use the potty and maybe have a drink of water and a snack, then if we like we go back outside.
The routine will be hardest for you, but it will be so worth it once you've noticed that none of your girls are wetting themselves. Also, not waiting until the last minute as they grow older will reduce their risks for recurring bladder infections, vaginitis, yeast infections, and various kidney problems.
Good luck with the potty re-training.