I’ve only ever seen it done this way, mind you it’s far easier when there is nothing in your tank.
https://youtu.be/cHlwBgTbe8E
Please don’t try this with your electric angle grinder, these guys use air powered grinders for inside the tank as they get wet. I would have to assume the water acts as both a lubricant and a coolant.
I would assume the bidding of any acrylic would be the same in principle, make sure your using compound, staff with a courser grid and work your way up slowly to fine grit and then finally a polish, and don’t leave the grinder in one spot; always keep the grinder moving.
Sent from my iPhone using Tapatalk