Its a 30 second job, doesn't get much any easier. Just realize that the second you alter a fixure or extension cord, the UL approval goes out the window. That doesn't necessecarily make it unsafe if done right though.
Figure out if the fixtures are 2-wire or 3-wire, and buy your extension cord accordingly, strip it, wire nuts, tape, done. Just make sure you cover the stipped portion of the wire completely with the nut, and then tape the connection completely.