Cleaning the back of an unfinished maple neck
Apologies if this has been covered off before, but whenever I search for cleaning a maple neck, I always get info about cleaning/shaving the fretboard, not the back of the neck itself. I'm restoring an '89 VDY and the previous owner had sanded all the finish off the back of the neck. It feels great, but it's got pretty mucky over the years. I've cleaned the majority of it with 600 and 800 grit paper (dry), but it's still not perfect. I've also used some household cleaner and a toothbrush. I'm reluctant to put the clear back on until it's spotless, but scared to try a coarser grit for fear of altering the profile too much. Is there a trick I'm missing? Also, do I need to oil the wood before applying the clear?
As an aside, it has a very small crack at the nut. it's totally stable and doesn't affect tuning, but I'd like to tidy it up cosmetically. Any tricks for that?
Thanks in advance