Re: poop training?
Power struggles, holding poop until you're not looking, hiding, I've been through all of that. My daughter went full time undies at 25 months, with very few issues, until her twin decided he wanted undies too 3 months later. He was also the kid who would wiggle and jump away from the toilet the minute I got him near it. I decided to focus my energy on her. One day he started snatching his sisters undies and I told him that if he wanted undies he had to use the potty, and he did. I wish that was the end of the story, but then my daughter totally regressed. She really liked being the only one in undies and it was very much a cry for attention and rebellion. What worked with her was constantly reassuring her that she was special and was a good example to her brother. I would tell her that we were proud of her for teaching her brother how to go potty.
When she has had times of frustration and wants to get into a power struggle she will have an accident. I admit to blowing my top sometimes, but eventually learned to just firmly tell her that this is not appropriate, take off her clothes, and hand her a prefold to clean it up. I will then help her clean it and she usually apologizes. You can't get into a power struggle over this. This is one of the few things that they can truly control, so you will lose every time.
As for my son, it took him a while to get it with the poop. I would get false hope because he would sometimes go and then revert to going in his undies. I could ask him 20 times if he had to poop, take him, sit him down, and the minute he got his pants up he would let it flow. What I finally started doing was going through the routine, and then not letting him out of the bathroom right away. With his pants back up I would start reading a book, or letting him play a game on my phone. Once he relaxed enough to start pooping I would rip his pants off and throw him on the potty. His undies would usually get dirty, but the poop would "plop" into the bowl for the most part. Once he realized that wasn't the end of the world he was more willing to cut to the chase and poop on the potty. If he went on a little potty, I would make a big deal about him getting to dump it into the toilet. I never imagined my twins would fight over who gets to dump. "My poopoo, my poopoo!"
Once you all get over these initial hurdles, just keep in mind that there can always be regressions. Don't take it as a sign of personal failure, or that your kid is slow, mean, careless, ect. There are so few things that they truly have any control over, mainly what goes in and what goes out. Most of the time, regressions are just their way of having control over something and expressing some frustration that they don't yet realize can be expressed some other ways. It can be misleading that they are usually pretty verbal at the point at which they are training. Just because they can talk doesn't mean they can really put their fears, emotions into words, for themselves, let alone for us.
So next time you feel yourself getting frustrated, stop and ask yourself why. Is it the mess, the fear that they will never, ever get it? Are you worried what other people will think? Once you address your own anxieties, you can start to see what will help your kids get through what must be a major, life-shifting process for them. I just think about how anxious I would feel if I was handed a pack of diapers to wear and told that this is how I would have to use the bathroom from now on. How long would that take getting used to?