^Yeah, it's already amazing that you're doing it, period. You have to be realistic about the pace you choose to go with though, having lots and lots (far more than I wish I did) of experience with the w/ds from both substances, simultaneously & seperately.. It is do-able, but it increases the risk of a relapse by an enormous amount. Especially the benzo withdrawals. When the acute w/ds were over for me (the first time around, when I stayed clean for 1,5 years), the PAWS lasted for so long that it was a gigantic trigger and made it SO much harder not to use.
How long have you been taking the sub now? I'd be careful (having experienced methadone w/d for the first time recently I now know what many people on here have said to be true for me as well, namely that long acting opi's are even worse than H or oxy to kick due to duration). I'd consider how long you've been on the sub and how long you intend to stay on them right now. If you're looking to use them long term to build up stability, that's okay, but think it through. You don't want to end up going through a sub withdrawal right after going through oxy/H withdrawals because you accidentally used the sub a few days too long. So if you're planning to use them longer than a week - 10 days, make sure you take it slow with the subs as well. Though, the longer you keep taking them the longer the w/ds will last. Anyway I'm sure you know what I mean, it's just something to consider.
Of course, a few days too long won't make you get a whole month of fullblown sub withdrawal, but it's not something I'd want to experience right after going through the acute withdrawal phase of a short acting opi.
Personally I would probably tackle the opioids first, and then when I'm relatively ok from that (however long that takes), do the same with benzos. To quit opioids (if I have suboxone and come from a short-acting opioid, I wait 4-5 days before my first dose and never use more than 2mg intranasally, otherwise it doesn't do very much for me unfortunately). Although to be perfectly honest, I have no intentions of quitting benzos, not in the near or distant future anyway. Not the way I'm looking at things now. I'm just talking hypothetically, if I were to. (I have many times before, & tried many times more)
The reason I wouldn't even try unless I could taper them one after the other, is because I really can't handle the two together when they are both quite severe.. The insomnia, paranoia, heavy anxiety and eternal duration are too much for me to handle. Most I can do is taper in the mean time (don't recommend it unless you have no choice). I just can't go cold turkey or take the final step to no benzos during opi w/d. The anxiety and the insomnia pretty much drive me CRAZY after a while,
not to mention the dozens of other w/d symptoms and the crushing depression that comes with it.
So if you can avoid it at all, taper them seperately, or if you must do it at the same time for some reason, please take it real slow. Not just for potential danger from quick tapering, but also because of the big increase in relapse chance that comes with it. Scheduling a taper lasting several months might be discouraging and seem like a long time, but getting clean in 14 days time, and then relapsing 10 days later because it continues to feel like the w/ds aren't getting any better is just as, (or probably even more because you'll have to start back from scratch) discouraging. So yeah that's why everyone always stresses that it's best to take the necessary time from the get-go and to be realistic about it to yourself and to the people you'll be close to during your taper.
Doing so will increase the success-chance as well as make it more bearable to do in the first place. Anyway, I've rambled enough off topic in here for now. Hah. Will put up some NSFW tags so I don't have to infract myself.
Once more, best of luck man and (if this place isn't too triggering for you) keep us updated with your progress!
