Where you have to use energy to do little more than push your idling foot over the top, with his technique Anquetil was not only pushing his working foot over the top, he was also applying the same power to his cranks there as he, you or anybody else could apply to the cranks at 3 o'c.
Exactly. The whole idea of maintaining power for more of the pedal stroke is to reduce the down-force at 3 o'clock, thus increasing endurance for the same power. So don't push your idling foot over the top, rather lift your toe and try to kick the dog off your front wheel as the foot goes forward over the top. Likewise, you can pull back on your heel cup at the bottom since your ankle's relaxed. Personally, I don't consciously push down on the pedals at all except for short periods on steep pitches.
Here's a good workout to help getting used to applying force all the way around the circle:
https://trainright.com/climb-faster-workout-cycling/
No upper body movement, as little bar force as possible, all done with the legs.