I sent Mark an email in case he's not paying attention here. Hopefully he'll chime in with better info than I can provide from my own experience and what he's told me.
Quartz has a much narrower working range than most glass, which is what I think he was trying to say above. Right near where you can work it, it will also vaporize, so it's a tighter situation needed to do it well. I usually hit the hotter side at least some, and have a white deposit nearby of condensed quartz vapor.
He uses hydrogen/oxygen, which I hear from a lot of places is the way to go. I don't have that and have used oxy-acetylene here with reasonable results.
Unlike you'd maybe think due to the small tempco, yeah you do have to anneal quartz work, or any work where there's any significant thickness variation or cooling rate variation. Always with boro glass -- always. Only on the very simplest pieces with no big thickness changes anyplace can you get away with the "carbon deposit" anneal, and even then it's not ideal. I've tested this on boro with crossed polarizers -- the Kohl book has time/temp schedules, that, unlike quartz, my heat treat oven can do. Quartz needs way above my 1000c limit for that. Mark? This is your domain, not mine!
Here's the old Kohl data on this, but the book I recommend elsewhere is better yet. Table on page 31 of the link (his numbering, not your pdf reader). But read it all.
I use oxy-propane for boro work with my little torch I made which uses a MIG (wire welder) tip for the gas tip -- works great. I use mapp gas in a big torch for pre heating larger work (up to an inch or so) and have no experience with larger than that. Acetylene is way way too much btu/second for boro glass and not usable with reasonable skills on it.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.