Thumb sucking (how to teach other ways to cope)

My 4 year old daughter still sucks her thumb, which isn’t a huge deal in itself, but it’s basically her only way to calm down. In the past few months her emotions have ramped up (as they do at this age), meaning more tantrums and her thumb has been sucked totally raw every day. We decided a month ago to try to crack down on it because 1. It’s not good for her physically and 2. We feel she needs to develop better coping skills. Since we have started this, the tantrums are lasting soo long and she has an extremely hard time calming down. I sit down with her in the calm down spot trying to help her breathe deeply and calm down because she hyperventilates. But I can only stay there with her so long as I also have other children and things to attend to. Even when she’s finally calm enough to come out of the calm down spot, she’s never fully regulated because then every small thing after that reignites the entire process. I feel like trying to help her calm down is consuming many, many hours of most days at this point and it feels like no progress is being made. I’m exhausted. Also, we’ve caught her hiding, sneaking her thumb still and lying about it which is another problem. Should we just drop this thumb issue? Or do you have any strategies on how to teach little kids other ways to calm down?