There are other (simpler ?) methods for splicing wires.
If there are not too many of them, you can cut the wire, get a piece of heat shrink tube around the wire, solder the wire and warm the heat shrink around the solder in order to insulate it.
Another trick that does work even though it sounds strange, is to connect the wire in a secure way (use the method / connector you want) and wrap the splice / connector with a special self-fusing rubber tape made by Scotch: Scotch 23 (type "scotch 23 tape" on Google to find the datasheet).
The thing is magic as it will seal (and insulate) over anything permanently.