Yeah, I probably drug that out a little more than I needed to without getting my point across.
What my instructor was essentially having me do was; after I planned for a descent at cruise speed of like 125 he was having me keep the power in. That resulted in accelerating to 180 knots instead of pulling the power back to descend at my calculated rate of descent and speed.
What he should have done is stopped me during my planning and told me that we're gona descend at Vno or whatever and have me calculate it based on what speed we're about to descend at. Not plan for the GS I'm currently at, and then descent at a higher speed. That obviously would never work in a million years. He basically saying that if I plan for a descent at 125 and descend at 180 instead that it would still work out.
Now that I really think about it, the planning I used to do is plan for 500fpm. Say I'm cruising along at 135indicated with 180gs. So I'd add 11 knots to that, 146(Vno)-135. So plan for a descent at 500fpm at 191 and then set a descent rate of 500fpm and then adjust power to maintain Vno. That's what the POH says to do anyway, except they call for 1000fpm.
I think I tried the 3/6 or 6/3 rule once in multi and kinda stuck with it.