We are using a system of interest free balance transfer cards right now to successfully pay off some debt that had crept up over the last couple of years.
This doesn't quite answer your question, but my heartfelt advice is to get the card, move all your existing card debt onto it, set up the app and your direct debit to pay it off over the 12 months, then cut up the card and never think about it again. Put a note into your google calendar for when the interest free period is coming up (you'll also get a bunch of emails from them) and then if it's not cleared by the end of the offer period, get on to money saving supermarket to get a new interest free card, and move the remaining debt there.
If you're at the point where you're juggling these cards, you've got to stop using them for anything.
We're not adding to our debt at all any more, and everything will be cleared in just under a year from now, which will be such a relief.
We have a couple of these cards, with different expiry dates on their offers, and it's all in a spreadsheet with google calendar alerts so we always know what we owe, and when offers are expiring. It's definitely a slog, but it's great to see it working.