Tiny, By using the Zim wrench you can hold the feeler gauge in one hand and use the other to hold and turn the wrench. You use your thumb to turn the adjusting screw while the rest of your hand hold the wrench. I've got a Snap On wrench that is similar to yours that I use. It does take a bit of practice, you need to have a limp wrist to make it work. With the idle turned down low it will still want to bounce your tool and hand of the rocker arm. Once you get the feel it will be easy. At first you will think its crazy.
Good Luck
Don
