I'd be tempted to try something like Simple Green and some clean rags before I'd try a solvent based cleaner? That's what I used on our pack's wooden track, but it's polyurethane coated, not painted. Just dampen the rag, not dripping. Not knowing what kind of paint it is would be a concern. TBR gave some good advice about trying anything in a small, non-critical area first. Stop section or underside of the track if it's all painted?