how is airspeed reduced if no speed control instructions from controller?

[what next]

How do you know? You´re not supposed to hear it!

I was taught flying jets by a guy (maybe the same one who taught you) who used to pull the circuit breaker of the overspeed warning and fly flat out until past the outer maker... Probably can't do that in a Lear because it will go supersonic But really: If you want to fly slowly, take a Cessna 152.