Thrust lever movement should be positive, on take off after 50% N1(CFM) or 1.05 EPR(IAE), just take it to the next position desired without any hesitation. The FADEC will take care of the engine, slow movement of the T/L is not necessary.
On landing with A/TH on, the ONLY reason to take the T/L to idle is to disconect the A/TH, it should be retarded immediately to idle, no reason to delay or do it slow.
Your Airbus Instructor is right on!!
G