I've used loctite/super glue on my thumb screws.
Use 1 or 2 drops and invert them.
Works a treat! No marring. Easy fix. Have only used it for eyepieces/extenders etc not on paintwork (probably too hard)
Wilso - wow I had no idea I could do that! The reason why I'm asking because I'm so sick and tired of my guidescope being scratched bit by bit so I'd lile to replace them with nylon tipped screws to avoid that. I currently have the guidescope rings that hold my orion 50mm guidescope. Also looking for a replacement focus lock screw for my William Optics ed70