Wellllll, its not exactly their belly that you're supposed to rub

Gently massage their "privates" with a warm damp cloth until they go potty. Do this every time after you feed them. I usually hold them over the trash can when I do it so it all will fall in there (sometimes there's a LOT).

Don't be worried if they are a bit irregular. The formula will most likely constipate them and/or give them diarrhea. Its a big change in their system to go from mama's milk to the formula, but they'll get used to it! They had their mom's colostrum for at least a week and that first few days is the most crucial for that - so that is really good! They should be just fine.

I feel so bad for the mama cat But I would have done the same thing as you.

If you have a portable radio, I like to play quiet classical music for my bottle babies (or sometimes radio talk shows).

You also may want to cover the crate or box they're in with a light sheet, especially when you are travelling with them. That will prevent them from getting a draft.

Sounds like you're doing great - keep it up!!