Well, actually, not wanting to offend and hating to be the bearer of such news, but given that you're asking there have been a zillion discussions of this task on this forum.

Basically, most contributors to the discussions have agreed that not all flare-nut wrenches are alike. Many brands are neither sized precise enough, nor robust enough (to resist opening slightly) -- the concensus, IMHO, is that Snap-On flare-nut wrenches are the only ones to use for this task, although some have also suggested the *old* Craftsman as well. Snap-Ons are so precise that sometimes I need to gently tap them (with some tool) onto the "nuts" if my treatment (below) didn't shed all of the dirt, or that the "nut" itself wasn't precisely sized. I'd rather have a slightly too-tight wrench than a slightly too-loose one, of course.

I've never had a problem with these fittings, preferring to replace the flexible hoses routinely upon buying a new (used) 240; and also occasionally having to replace the calipers because of the usual problems occurring on such old parts.

My own protocol includes (1) initially liberally spraying the area of the nuts involved with Brake-Kleen, just to get rid of a layer of dirt. (2) spend a whole day repeatedly (about once per hour) spraying with PB-Blaster. (3) the next day, I can put a Snap-On flare-nut wrench on the fitting to the caliper, or two wrenches if its the metal-flex hose junction (and with a firm squeeze of the wrenches in my hand), easily free the fitting without rounding. No torches needed.

But the key, really, is the SnapOn-brand flare-nut wrenches -- they're the only ones I trust for grasping these soft-metal "nuts" securely enough to turn them without slipping and rounding.