I love using those heat-shrink solder plugs for splicing wires too. (at time mark 15 min) I go a step further by slip a separate piece of of heat-shrink tubing over the one side of the wires before I install the plugs. After I have installed the plugs, I'll then slide the other heat-shrink tubing over the plugs to help seal them. To me it is a lot cleaner looking than using electrical tape. Then I may use a wiring loom to finish the whole project.
