What I've always done w/ my +2 on. Is just buy a 120 link chain. You have to cut some off, but takes the guess work out.
I don't remember 100 on the stock brake line, when I got my +2 I just decided to buy the extended brake line.
The only tool I can think of that would help make this process easier is a snap ring tool On the carrier there is a big snap ring. you CAN get it out w/ other tools, but to make it quick and painless this is by far the easiest way.