Use The Pool Calculator to calculate an approximate dose. Going from 8.2 to 7.6 with a TA of 145 in 27,000 gallons says it takes 52 fluid ounces (6-1/2 cups) of full-strength Muriatic Acid (31.45% Hydrochloric Acid). The more accurate amount would be closer to 60 fluid ounces, but your pH measurement is approximate anyway.

Add the acid very slowly over a return flow with the pump running and after you've added it, lightly brush the side and bottom of the pool in that area to ensure thorough mixing.

Since you will probably be shocking the pool with chlorine to clear it, I'd lower the pH even more to around 7.2 which would take (according the The Pool Calculator) 112 fluid ounces of acid. The added chlorinating liquid or bleach will raise the pH when you add it so starting out with a lower pH helps out.