I'm replacing my flexible brake lines. I've removed them from the calipers but am having trouble removing them from the hard lines. I've soaked them several times in PB Blaster and have an 11mm flare wrench, but even with that the hard line nut is starting to round off.

What's the best approach to breaking this free? Should I use the 11mm flare wrench to hold the top nut in place while turning the 17mm soft line, or vice-versa?

Any other tips on getting this done without ruining anything? Thanks.