Do a search on here for magic eraser. That'll get you started.

That art looks worn too thin for a Magic Eraser. He'll just end up wearing down to the wood or lifting chips.

Yeah, I heard to stay away from using magic erasers, something less abrasive....

Well, there really isn't much less abrasive than Magic Erasers, that's their purpose. Fine wet sanding. The issue here isn't so much the tool as it is the playfield. That playfield looks like it has some really think ink from wear. You can see little flecks of wood all through the playfield. There is a good chance the ME would just sand right through the remaining ink. IMO this one looks more like a touchup candidate than a sand/clear.