....Also be sure to use rosin core solder for any splices and double wall heat shrink, the stuff that has glue in it so it seals to the wire insulation. I usually us a double layer for under hood splices, small heat shrink just big enough to slip over the solder joint about 1" long - shrink it then slip a bigger diameter heat shrink over the smaller one once its cool. Make the bigger diam. shrink about 3" long this provides excellent support and sealling for the splice.
I use the Rosin core and the HD heat shrink (with the glue inside) but I had never thought of doing it as a two layer setup, sounds good, thanks.