[Too Many Projects]

I have one of those and they are better than an open flame but he STILL needs to be careful with heat and brake fluid. It tends to expand a lot when heated above it's boiling point and can burst flex hoses.

Keep a wet towel around the brass block and lines you don't want heated and focus on just the flare nut to break it free. A propane torch will work, but keep the flame short and very sharp with just the point on the nut.
Also, and you probably know this, but use a line wrench to minimize distortion and slippage around the nut.