A small pick is an essential workshop tool. I have been using this small pick for a while and could not build without it. A common problem while cutting outer cables is they get crimped as they are cut and often the lining gets flattened. Use the pick to open the cable back up and widen the lining. It is very important to make sure there is nothing preventing the inner cable from running smoothly through the outer. Have a look at the images to see the difference.
Also great for locating internal cables for dynamos and brakes or gears.