We're in full potty-training mode here. Mia and Aidyn, age (almost) 34 months (aka two months short of three years old), are learning to use the toilet. And I can tell you, two kids learning at once is at least one too many. Fortunately, it happened that Mia caught on first, so we went with that and helped her before focussing on Aidyn. Not that we (the adults) have really made any choices here; in fact, I hesitate to even call it "training." My role is to help them practice and learn to do something we adults expect them to do but which we've "trained" them NOT to do for almost three years. Thinking of diapers and potties and trainees and trainers this way I feel gives me some perspective.
At first, I thought I could "train" them. Take the diapers off, give them a few days of peeing everywhere and they would learn. But two kids peeing everywhere is taxing to the soul, and the washing machine (I swear we wash towels every day), and all anybody learned was that they didn't want to go to the potty. I considered bribery. Candy, not so much: I can't give them candy EVERY TIME they go in the proper place. Aidyn pees about 1600 times a day! So I bought stickers. In the store, "YES! YES! We want!" At home, with the potty association, no interest. Hmph.
I felt completely powerless. How were we going to get this done??
Well, we're not done yet. But every day brings more and more success, and perhaps more importantly: I don't care. This is not a problem I need to solve. Even if they're not diaperless for preschool, there's no law against it. I don't need to feel time or any other pressure. And by taking it out of my hands and putting it into theirs, maybe I've given them what they need to get the job done: control.
Here are my more-or-less concise points for your guidance, interest, or amusement:
You're not training, you're facilitating. Helping them to practice-practice-practice. The ultimate decision to take the diaperless plunge is theirs alone. Still, they're not going to do it overnight. They have to learn, and to learn anything, you have to practice. This we can help with.
--I remember always thinking this was bullshit when I read it in the books, but now I'm for it. You choose, you stress. They choose, you...clean up. But you stress less.
If one does it and the other doesn't, CELEBRATE! One is definitely easier than two. Embrace one-at-a-timeness.
DON'T tell them it's potty training, or they'll balk. How do we forget that we're talking about terrible twos here?! Just like everything else in their lives right now, THEY want to decide. Trying to force them will just bring on a tantrum or, more generally, the opposite of what we want - in this case refusal to use the toilet.
DO encourage them to go without a diaper, even if it's just for a few minutes. This is their practice time. They will build on it.
DO let them choose to put the diaper back on. I think this is part of the terrible two factor. Give them some control.
DON'T just let them pee all over the house. You'll go crazy and they'll just have fun sliding around in their own piss. I gave them half a day and then gave up. A couple days later, we did half a day again. And so on, with more frequency and longer as they wanted/could. I think this is the best practice and also gives them time to develop the resolve and confidence they need to complete the process.
DON'T believe that "pull-ups" are like underwear. They are diapers. You can take them off and put them back on like underwear, but for kids they are diapers that they can pull on, pee in and take off like underwear. We HAVE used them for their ease of peeing in and out of, but don't expect dryness while they're wearing them.
DO give them underwear. Either the sensation of being wet or the pride of wearing underwear seems to help - who cares which it is! I'm a big fan of nudity but that seems to encourage "pee anywhere" habits.
When they both scream "I pooped!" DO assume that both have pooped and not both in the toilet.
EVERY KID IS DIFFERENT. Your first and second, your twins, my kid and your kid. They will all do this and lots of other stuff in surprisingly varied ways. But some things, maybe small, maybe big, will correlate, and our experience will overlap.
That's it for now. If I think of anything else, I'll let you know.
Good luck, to you and your kids!