bad scale deposits from not opening pool last year

[Cobra10thaniv]

I have terrible scale that I finally scrubbed down and is mainly in the hopper section of pool sides pretty clean but a cpl of small areas. I have dropped the ph down to 6.2 alk to 80-100 total hardness to 200-400

I still have sand like scale I can get off if I scrub a area 1"x1" but the 3 years to get it done isn’t going to work. I live in the country so I can lower the water level and refill easy. What chemical can I use to aggressively remove the scale. All the main stuff has flaked and come off.