the cones usually have flats for use with a cone wrench (usually 15mm, IME) to immobilize the cone as you tighten down the lock nut (usually a 17mm), In my experience, the cone tends to back out slightly as you tighten the cone and the lock nut against each other (which might be just the way I do it), so I tend to over tighten the cone slightly, to the point that the rotation feels a little rough. Then, when I tighten down the lock nut, and the cone backs out slightly, I usually hit the sweet spot. Might take a couple of goes before I get it just right