Lighter fluid is indeed naptha, but it's unlikely to dissolve whatever's on your neck. It'll just clean it. If the "grunge" is lacquer, then acetone will do it. If it's glue, then acetone or toluene may do it. If it's polyurethane, then good luck. MEK (Methyl-Ethyl Ketone) may do it, unless it's cross-linked. Then, you're pretty much stuck with sanding/routing/chiseling it off. Stuff is sturdy as hell, which is why it's such a robust finish. Be aware that all those chemicals are highly combustible, and you don't really want to get them on bare skin, either. Wear gloves.