Plastic tape (look here: http://forum.slowtwitch.com/...stic%20tape;#2919777
) works better than electric tape. It doesn't gum up like electric tape does under sweaty hands.
Tom D. alluded to this in his description, but you want to wrap the two sides in opposite directions. Just as with a normal roady drop bar, you want the tape to tighten on itself when you pull on the bar. Since you'll be wrapping from the shifters or brake levers back, the tape goes out as you go under the bar and in to the center as you go over.
Overlap about 1/3 sounds right. Most tape that I've used is thicker in the middle so the overlap leaves a relatively smooth surface when you're done.
You're right the start is the tricky part. People like Tom who've done this countless times can probably do it with their eyes closed. I make an angled cut and do a couple of dry runs to get the angle right before I tape the end down. I also use the fitted piece to cut the other side, remembering to hold the pieces back to back since the tape will wrap in the opposite direction.