What are some proper punishments for my kids?

My boys are TERRIBLE for doing things the first time you ask. It’s driving my husband (their step dad) BONKERS. Probably one of the biggest things to start a fight with us honestly. I will say go get into the shower please and kid will say ok but then pick up a toy and look at the TV or walk over and pet the cat and say “I just gotta pet him first cause he’s so cute”. My 11 year old is ADHD and he’s a big space cadet. He’s medicated for it and most other things (besides being unreasonably loud and always making some sort of weird annoying sound) is very well behaved. He is not defiant at all. He’s not destructive or mean or anything. He’s just… ugh… so hard to get him to do something! Like I have to ask 5, 6, 7 times and finally yell “GET IN THE SHOWER NOW! NO MORE CAT! NO MORE TV! STOP PLAYING WITH YOUR BROTHER FOR THE LOVE OF MAN AND GET IN THE BLOODY SHOWER” and THEN he goes uh oh OK and goes to the bathroom. He does this with EVERYTHING. Sitting down to eat, going outside to play, putting stuff away, anything. His 8 year old brother is way better than him but not great. Not near as bad but still pushes it often until I raise my voice. The problem is that he has diagnosed anxiety and so often if I finally lose my cool, he shuts down and starts crying. And if my husband loses his cool (which is often cause he’s not a super experienced dad), the 11 year old gets some major attitude (which makes my husband more mad) and my 8 year old just starts crying. SO I need some suggestions on how to manage this behavior that is mostly universal for both kids. I understand tailoring punishments to each unique child but what can I do that is similar to each to try and establish a better “House Rule” regarding listening? It’s tough cause again, they are BRILLIANT (high achieving, above grade level learners), kind, and generally very very well behaved children. They’ve never broken anything or even drawn on the walls or hit someone out of anger. Like they’re honestly so good so I feel like a MONSTER when I give them punishments for being “spacey” but also like this is real life stuff that they need to work on. I have so much mom guilt and when my husband raises his voice and the kids push back or cry it just tears me apart. Also yes, he is working hard on his temper and so am I. We’re both in therapy and making progress. We’ve come a long ways and know that we don’t need to yell but we always seem to resort to it after the 17th time of asking for something and getting nowhere.