I have always just snapped them open, it usually works fine but there is an ocassional bad break. Thanks for posting that source for an opener it is a good idea. If I used amps a lot I would think it would make sense to get one, they are cheap.
Another guy before mentioned a glass filter or something like that, to filter out any small glass particles that may have fallen into the amp when it is opened. I have always wondered about that? It does seem like it would happen, when the amp is broken.