Everything Steve said is on the mark!

But to clarify his "quality flare wrench", I'd suggest that there is only one that is precise enough. Find a Snap-On jobber's truck and buy their flare-nut wrench (of the size you need). Anything else (e.g., Sears, etc.) is apt to be slightly loose, and it's really easy to round the nuts.

And one more thing. I like to spray liberally with CRC Brake Cleaner, only to remove all debris, road grime and other deposits, before using PB Blaster -- this ensures that all the PB Blaster is soaking into the threads instead of being blocked. After cleaning the area with the Brake Cleaner, then spend the next 24 hours or so periodically (every hour or so) spraying with PB Blaster.

I've done it this way on New England cars with as much as 25 year old original lines, and they come right off, even without propane torching.

Good luck.