There are two tricks to lowering TA.
1) cycle between 7.0 and 7.4.
2) Make LOTS of VERY tiny bubbles.
I got a sump pump, put it in a bucket to protect the pool, and built this on top of it. I drilled 5-10 1/4" holes in each cap. I can lower TA by 10 in 12 hours (30K pool). You can probably do 10 in 8 hours. You should build something like this so you can get your TA down when you add more water.