I ordered new rear disks for my W123 - They came and they were wrong ones

They were fronts. Costs more to return them than what they are worth. So I need another set. But for the coming winter I think I can get by with existing. However, I would like to clean them up. They are almost full thickness still, but have rust around periphery that has been grinding pads away and causing rough braking.
I have seen several Youtube videos on resurfacing using regular tools. I might try that, but have a question:
Has anyone used abrasive cleaning pads? The 107 FSM shows them in section 42-260. Dealers used to use them when customers had complaints about brakes pulsing. Looks like they are still available - at a price ($123 list for 4)!
Wondered if anyone had tried to make something similar using old pads?
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Graham
85 300D

,72 350SL, 98 E320, Outback 2.5