wise to stop when they really won't move, cause they do snap.
You should start by trying to shock the caliper right around the bleeder screw. If that doesn't work, you can try carefully tapping a SIX POINT socket or wrench forward and back on the screw to try and break it free. If that fails too, heating up the caliper around the bleeder screw should work. That'll screwup your painted finish on the calipers though... but may end up being your only option.
yeah a 6pt socket or box end wrench will provide alot more grip than a flare nut wrench since they still flex out when you torque on them... they are ideal for fittings where you can not get a box end or a socket on due to a line running off the back of the fitting....
dont forget the pb blaster.. .. lube em up with that..... tap around the screw... do it the next day and the next da for as long as you want... the more you soak them and tap on them... the better your chances of getting them off will be
I had speedbleeders on my old motorcycle... and they leaked. I ended up getting new bleed screws from Honda to replace them. Really the best thing you can do to make bleeding the lines easier is a vacuum pump.
Back on topic, I think he's more worried about snapping the end off the bleeder and leaving some stuck inside the caliper. That can happen no matter what you use, it happened twice on the Mazda I was working on over the winter (both rear calipers). Just a little lube, heat, and patience, you'll get it.