For temporary use outdoors use a plastic bag, preferably a heavy polythene that is UV resistant, as a cover, and a cable tie and tape to keep moisture out. For sockets put a plug in there, and wrap with some pipe thread tape ( so it will not stick to the threads) and then self amalgamating tape, or the nice new silicone wrap that only sticks to itself, then wrap overall with 3M insulation tape.
For more permanent use the same PTFE tape and silicone tape, but use some self amalgamating tape over the outer, followed with the 3M tape. After a few years when you cut the tape the inner is still shiny bright.