Kai,
For what it’s worth, I recently restored a very badly scratched and scuffed Beogram 1800 dustcover to like-new condition using micro-mesh cloth and following the instructions others have posted on this forum (thank you all who did, by the way; I’m deeply grateful!). If you are just dealing with light swirl marks or fine scratches, a liquid polishing compound might be sufficient. If your scratches are deeper, I found micro-mesh cloth really does work. As many others have said, the trick is to start with a course enough grit to remove all the original scratches, sand in only one direction per sheet, switch directions 90-degrees between sheets, and don’t step up to the next finer grit until all you have are sanding marks running in the same direction. In my case, I was dealing with a turntable that had spent several years neglected in a dirt cellar and which suffered some pretty deep scratches and gouges thanks to having other things stored on top of it. It took a couple of hours sanding left-to-right using 1800 grit micro-mesh cloth to get all the original scratches and scuffs out and leave only my own sanding marks remaining. I then progressed to 2400 grit and switched directions 90-degrees by sanding up-and-down. Once the 1800 grit marks were replaced by the 2400 grit sanding lines, I moved to 3200 grit cloth and went back to a left-to-right sanding direction. Over the course of a couple weekends, I eventual worked my way up to 12000 grit cloth and then used a micro-gloss polishing compound to finish things. It was tedious, involved a lot of elbow grease, and was a constant struggle to avoid the temptation to step up to the next finer cloth too soon. To be honest, I actually gave in to that temptation the first attempt and had to start over again before getting satisfactory results. Not sure if the attached picture does it justice but the dustcover now is smooth to the touch and clear. Like a dummy, I didn’t think to take any pictures before starting this restoration project but initially everything was caked in a fine, red clay dust, there was a good deal of corrosion and the dustcover was in very bad shape. Using the advice and instructions posted on this forum, I was able to get this turntable functional again and looking close to its original state. Best of luck with yours and rest assured that the techniques people here have described really do work if you are able to take the time to follow them.