If your fill water is high in TA, then you need to wait until after you're finished lowering your CYA before you adjust it--otherwise you're lowering TA by aeration and then raising it right back up again by refilling--a waste of time and money. If the fill water is low in TA, then the draining/refilling should help lower the TA.

My bigger concern in looking at your numbers is that Cl of 3 with a CYA of 100 is nowhere near enough chlorine--you should keep your Cl no lower than 8 ppm if you don't want to chance an algae bloom.

Janet