Electrical tape to finish, with the Fizik finishing tape over the top is the way to go. Also, use electrical tape to hold the bar:gel pads in place, as the glue on them is tacky, rather than sticky. Wrap, unwrap and wrap again if unhappy is the key.
Once I'd finished mine, I singed the ends of the finishing tape with a heated screwdriver blade, makes it less likely to come undone. One other nice wheeze is using sections of old inner tube - cut and thread onto the bars before fitting tape, then place over the ends of the tape nearest the stem once you're done. Never done this myself because I didn't fancy taking the levers off. May do it if I ever fit new bars though.
Also, don't get knocked off and ruin the tape scraping it along the road just a month after fitting it.