The Craftsman reversible ratcheting combination wrench makes the job a lot easier. Craftsman makes two types of ratcheting combo wrenches. I recommend the more expensive version with the reversing lever. It has a fine tooth ratchet. The other version is too course to work in many applications.

You also might need a glow plug reamer, which you won't find at Sears. I have used a drill bit of the appropriate size, twisted by hand. When you finish reaming, turn the engine over with the starter to blow out any leftover carbon. (Before installing the new glow plugs.)