Be honest with ya its a wast of time and money...
brake lines rust from the out side in..Calipers freeze up when the dust cover or boot get tore and get contaminated or when the piston or seal wears out and gets oblong..I never seened moister in a hydraulic brake system..Air brake system on heavy truck yes but hydraulic never.

 

Brake fluid absorbs moisture. You said it brake lines rust from the inside out. Why is that. Brake fluid becomes more corrosive when it has moisture in it. My 2 cents

 

I gave the factory service manual a quick read and it says you need to use a computer to purge the ABS unit. Is much missed when not doing this? I just did the front calipers and used 1 litre...need to get another to finish the rears. I would have used less if I had run the reservoir dry before topping it up. The new and the old really mix.
I'm hoping the poor braking performance is helped a bit by doing this. My truck is 10 years old and has 215,000 km on it. Changing all discs and pads a couple years ago did not help.
Steve