Jewelry retailers are quick to update their websites, their inventories, even the lightbulbs in their stock room. But getting staffers up to speed on the latest selling techniques is a responsibility many retailers tend to shirk.“Owners simply can’t afford the time,” says Pat Henneberry, president and founder of TheJewelryCoach.com, a new online training resource. “They’re doing it all—the marketing, the business side. And all of a sudden, there’s a new jewelry brand in their case, the salespeople have no ­knowledge of it, and there’s no one there to train them.”It’s easy to forget that the diligent folks selling your merchandise require more maintenance than your store’s Facebook page. And owners who aren’t involved in day-to-day selling may not even realize the degree to which an employee’s sales skills are lacking. There are a handful of respected train