pull back the outer insulation, make the connections and then push the outer insulation down over the three wires.

The way I do it is to grip the three inners in a vice and pull the outer back by stroking away from the vice. Strip the wire and make your connections. Then do the opposite. tie the cord over a post at least six feet away from the plug and milk the outer back over the inner three. The last step is kind of like the way you finish off a double braid splice.