I built my road bike from parts. On my commuter bike (on which I don't commute), I replaced the upright bars with drop bars, which required changing out the brake controls to special drop controls that would allow for the extra travel necessary for V-brakes, and replaced the twist shifters with bar-end shifters. I've built the wheels I ride on from parts. I break my road bike down to parts annually, clean and lube it, and rebuild it. I replace my own chains, possibly too frequently.
I thought I'd do my wife a favor and replace her black cable housings with blue ones to pick up the blue highlights on her bike.
I completely underestimated the difficulty of the internal cable routing.
Laura OLPH wanted to do a bit of wrenching, so I invited her over to see the process. We started with the front brake, which was straightforward. But when we went to run the cable for the back brake, we had a modicum of difficulty fishing out the cable at the seat-tube end. We set up the housing, adjusted, and tightened the brake, and checked it. The brake would not release.
At first, I thought the problem was in the brake, so I added a washer in the brake mechanism. That made only the most minor of differences. Then I thought the problem was the run of housing between the seat-tube and the rear brake; I cut another piece of housing, and that wasn't it. Laura noticed that the cable wasn't entering the bike straight at the head tube. I thought it was the flexibility of the housing I was using, so we re-used a piece of the black housing that I had taken off. It worked.
Laura later spoke to the guys at Hart's; the problem wasn't the flexibility, it was that I was trying to put a 5mm ferrule (the cap at the end of the housing that protects the end) into a 4mm hole. Knowing that, I tried to replace the piece of cable between the seat tube and the brake, and wound up messing up the system again. I finally broke down and brought the bike to Kim's, where, no doubt, they have the goods to do it.
I've been researching ways to do the internal cabling; some suggest dental picks (which I have); another uses thread and a shop-vac; or thin tubing. This last seems the most reasonable to me. I found some housing liner at one of my online suppliers, and we'll see how that works. (Before I do, though, I've got to check my replacement cable sets to see if they supply 4mm ferrules for the brake cable; I've proven that the [previously] more-or-less standard 5mm ones will not work.)
It was a frustrating day.
Edit: In addition to the tubing that can be used to thread the cable, I've ordered samples of three sizes of ferrules to see how they work. I'm going to either learn this, or prove that it's completely impractical for the home mechanic.