The visual background and lighting over your stove may make it difficult to see the "shimmer," or perhaps your eye just needs some practice. Whatever. Let's work around it.
Forget the wooden spoon.
Put a little oil in a cold pan, off the heat. Move the pan around and see how thick the oil is and how slowly it moves.
Empty the pan, discarding the oil. Wipe the pan with a paper towel, getting it as dry as you can (if you're OCD you can wash it), and put the dry pan on the heat -- at medium-high -- to preheat.
When the pan is -- in your opinion -- preheated, put a little oil in it. Swirl it, and see how it moves. If it moves like water, and doesn't leave any dry spots -- it's almost, but not quite ready. Put it back on the heat for another minute or two and it will be saute temp. "Almost, but not quite ready" means it would be better to give it ninety seconds, but it wouldn't be a tragedy if you started cooking.
It's more than likely that you won't wait long enough for it to fully preheat. Don't worry about it. If the oil doesn't move freely, wait until it does, then add that 90 seconds.
If it barely smokes, it's more than ready to go, add your saute ingredients immediately.
If it smokes a lot, it's too hot. Let it cool briefly off the fire, empty and discard, wipe and start over.
Some people put a little water in the cold pan, put it on the heat, and assume the pan is close to ready when the water completely boils off. Not a bad idea. Sprinkling a little water on the French top is an old restaurant trick.