Use two of each wrench. On the front, that's two 17 mm combination wrenches and two 13 mm cone wrenches.
This is from Sheldon Brown's site:
Faster With Two
Even when two identical cone wrenches are not essential, they are a great aid in adjusting the cones quickly and exactly.
If you do not have two of each needed size, to make even the smallest change in the cone adjustment, you must first loosen the locknut, then adjust the cone, then re tighten the locknut. If you get the cone adjustment just right but the locknut is not sufficiently tight, tightening the locknut will throw the cone adjustment off. Careful cone adjustment by this technique is a very time-consuming process of trial and error. (emphasis provided)
If you have two wrenches of each needed size, the fine adjustment can be done much more quickly and easily! First, get the cones in roughly correct adjustment, with the locknuts fairly tight. Now, if the cone adjustment is too tight, put a wrench on each cone and back the cones away from each other.
This will simultaneously loosen the cone adjustment and further tighten the locknuts. If the cone adjustment is a bit too loose, put a wrench on each locknut and tighten them together. This will tighten both the cone adjustment and the locknuts at the same time. This approach will enable you to make very small adjustments to the cones without loosening the locknuts.
It's really easy to make exact adjustments. Often the ends of the wrenches are moved just a few millimeters.
Here's the whole article.