I use a 'three wrench' method: I only loosen one side lock nut/cone. After cleaning/relubing, I hold the unloosened side with two wrenches (cone wrench and crescent usually). I adjust the cone on the other side, and then hold all three wrenches (two cone wrenches and crescent) while I tighten the lock nut on the 'loosened' side. It takes a little getting used to, but once you get a feel for it, it is pretty easy.