I agree with John. I did rear shoes a few days ago and used a c clamp as well.
Also, if you are replacing wheel cylinders the lines will come out without damage if you have patience. It took me about a day per wheel cylinder/shoe, but I didn't want to chase lines up to the front of the car knowing my luck, so it had to come out at the fitting. It probably would have been smarter to work at both lines in the same day, but it was too cold.
Basically what I did at first was spray the fittings with Kroil (or PB) and let it sit overnight. Then on each side I pulled the bleeder out with a six point socket and got on the fitting with Irwin 4LW Vise Grip pliers. Slowly work the fitting back and forth. Maybe a few light/medium taps here and there with a rubber mallet. Then occasionally I would switch to the flare nut wrench, just to maybe give it a little different force. The pliers/wrench will slide on the nut slightly, but if you're gentle it will not round the nut. Continue to spray the lubricant on the fitting. I wasn't having luck the first day, so again I let it sit overnight with the Kroil on it. This may have been the key. Put the bleeder back in obviously. The next day I again worked with the Vise Grips until at some point I felt the fitting tighten. This is the important here, the line tightened first, I doubt it would have loosened first. Then once it tightened I got the flare nut wrench on the line, soaked it with Kroil, and worked the fitting back and forth until it came free. Both flare nuts had a little bit of rounding damage from the force, they won't come out perfect, but still were square enough to loosen and tighten the fittings without issue. If they need to come out again in 100k miles then the lines will have to come out anyways. I hit them with black spray paint because the protective covering was starting to peel in places.