If OP is a heavy user I don't think a couple milligrams of Xanax is going to do much against fentanyl withdrawals.
Did you mean to write "quit without going cold turkey"? I guess that's what you meant because you're asking about tapering.
Also, I know you just said you don't want to take subs, but I have to ask: Why not?!
Subs would be the best - and maybe only - option here. If the blue pills are indeed fentanyl (and not nitazenes or other shit) and you've been on them every day for months or years, you're probably looking at a relatively short but very unpleasant detox. Subs are very long lasting so you could probably get through the worst of it with just a couple of large doses. In any case, I don't think you can get through any kind of opiate withdrawals without experiencing some withdrawal symptoms.
In order to get good advice from people on here, it'd be good to know a bit more about your situation. For instance, the two key questions here would probably be 1) How long have you been smoking the blues? and 2) How many pills do you get through per day?
Good luck with it all. I hope you find some good advice soon.