But absolutely, reference point creeping up the canopy requires the airbrakes to be shut, and seeing it creep down the canopy means open them some more and/or sideslip.
Exactly!
I always taught power pilots, when teaching them to fly gliders, to handle the air-brake lever in the same way and same sense as a throttle, with the all-important proviso that once it is all the way forward, you will still be descending!