you can't really estimate with the power off. If the adjustments are plastic instead of metal, you may be able to use a small screwdriver, but its much safer to use plastic tools. I would most certainly NOT USE YOUR FINGERS. You are a path to ground. If your resistance happens to be less than a circuit nearby, dangerous voltage could travel through your fingers and your body, possibly causing death.
Always play it safe around high voltage, your life is worth much more than a small inconvenience.
