It was her photos that inspired me to make a handheld rangefinder card for the Trip 35. It certainly helps, but even so, I don't have her unerring instinct for the right distance setting. Forgive the iPhone photo:
You can ignore the hyperfocal distances for various apertures, and look at the top of the card. I hold the card in my right hand with my arm fully extended. Using my left eye only, I place the zero at the top left corner on the subject, then swap eyes (closing the left and opening the right) and I read off the distance of the subject from it's new place along the distance scale which is in meters. It works!