Lowering TA is a process and here it is in a nutshell:
1. Test TA and pH
2. Drop pH to 7.0 and not lower (lower can damage pools and equipment) It does not matter if you walk or slug the acid, it will have exactly the same effect. The act of adding the acid and dropping the pH is what lowers TA.
3. The trick now is to bring the pH back up without raiseing the TA. We do this by letting the CO2 created when we added the acid outgas. To speek this up we aerate the water any way we can.
4. When the pH is above 7.4 to 7.6 we test TA again and if it is still now low enough we repeat this process from step 2. When the TA is at target we stop and just aerate to bring the pH back up.
Here are full instructions:
http://www.poolforum.com/pf2/showthr...-HOWTO-amp-FAQ

If you are comfortable with handling Muriatic acid then the acid demand test will be helpful in getting the pH down to 7.0 quickly without overshooting.

The only time you get into a vicious cycle with TA and pH is when you try and follow a pool store's bad advice of putting a whole lot of acid in at once, usually by sligging it in the deep end with the pump off (which tends to drop the pH dangerously low and damage pool surfaces) and then trying to bring the pH back up with a chemical, which raises the TA back to where it was when you started or worse if you use pH up (sodium carbonate) which will actually cause the TA to go higher than when you started!