The sand paper thing does sound crazy to me, I recon it would cause more audable damage maybe they mean something like 2000 wet & dry ?.
I have thought about repairing a scratch before using a microcoscope and a fine scalpel guess it could be possible if you have the steady hand of a brain surgion
Alan
Turntable - Garrard 401/Jelco 750L/Ortofon Kontrapunkt B, Pioneer PLC 590, Micro Sieki MA505 , Denon DL103R - DIY Paradise Phono stage - Reel 2 Reel Studer A810, Otari MX55,Tascam BR20, Revox A77, B77, PR99, TEAC X1000 & 3440, Digital HTPC / Young Dac - Preamp - DIY B4, 821, Power Amp's DIY Avondale NCC300 Mono Block, Speakers Wilmslow Kit Volt BM220.8 / Scanspeak D2905/9500