They did work wilily - literally, “they also,” or “they too, did work, etc.” The “also” serves, apparently, to connect the stratagem of the Gibeonites with that employed by the Israelites before Ai. It hints that the Gibeonites resolved to meet craft with craft.
Rent and bound up - i. e. the wine skins were torn and roughly repaired by tying up the edges of the tear. The more thorough and careful way, hardly feasible in a hasty journey, would have been to insert a patch.