By the time I use a wrench on brake lines, The line isnt worth saving. I cut the line off flush with the fitting and use a 6 point socket. A cheap line wrench is a waste of money. Snap on gets kicked around because it is readily available and of good quality.
My BMWs' tool kit is a bunch of Hazet open ends. Fine tools,but the shipping is a killer.
If you tap the flats of the fitting with a small hammer and a punch, the fitting will back off easier. I can get most fittings on the BMWs off with my Craftsman open ends. I have had the fittings off before and they get a coating of grease. Vise grips are the last ditch tool. Too much clamping pressure and you will crush the fitting, making it oval and useless..
I have developed these work arounds, because I rarely work on brake lines. If I made a living with my tools , they would be better