You shouldn't ever raise the inflator button over your head. That puts undue strain on the hose and does absolutely nothing to help your ascent rates. What you should learn to do is when you are doing a vertical ascent you hold the button, and raise the inflator until the air bubble equalizes and the air just starts to flow out. Leaving the button open, as you ascend the air will automatically equalize maintaining your ascent rate. If you need to slow the rate of ascent down, lower the valve, if you need to accelerate the rate of ascent you raise the inflator. This takes a bit of practice, but there is never an excuse for raising the inflator over your head unless you are trying to accelerate the wear on your corrugated hose. Not a great idea and unfortunately this is the widespread idea taught in most classes on how to dump air out of your BC but is entirely unnecessary. The best solution is to only use the inflator hose as a dump on your initial descent from the surface, at 5-10' of depth trim out and then you're adding air anyway. At all times during the dive, use your rear dumps as needed then on your ascent stay in trim until you are 15-10' of depth and then turn vertical to check for anything over your head and use the dump method prescribed above. If you do it the way your instructor taught you, you will have no choice but to have a slinky effect on your ascent because you are constantly changing your state of buoyancy instead of maintaining a steady level of ever so slightly positive to keep your 30ft/minute ascent rate