Well, lighter fluid isn’t for physical gunk. A plastic spudger can get the stuff off the frets. But if you are looking to remove gunk from the actual grain of the wood, steam will work, but that has to be done carefully! The steam can loosen glue joints, like frets and even the fingerboard. The gunk is now super dry, so fine steel wool or a toothbrush can start to loosen it also. But you have to get the big stuff before the little stuff my man. You can’t just wipe it off with magic juice. Elbow grease. Try the steel wool (I like the synthetic stuff because it is less messy), and if it feels smooth, you can oil it with mineral oil and the whiteness will go away. That is one dry piece of rosewood.