easy adjustment:

1. leave a small amount of adjustment room in the barrel adjuster
2.release cable from clamp
3.hold both sides of caliper against the rim, by hand or by other means
4. pull the cable taut and tighten the clamp
5. turn the barrel adjuster to open the brake as preferred

the cable doesn't need to be real tight when you clamp it, just remove the slack while you have the caliper squeezed. 4th hand tool is great for other kinds of brakes, not really needed for road calipers