I love this thread 
While we are talking about file cleaning, this is what I do. Take
the file and warm it up over the alcohol lamp, then ‘file’ on
some beeswax…let it cool, reheat and wipe with some paper
towel…will take most of the gunk out. The stubborn gunk I get
out with the flex shaft and a WD-40 treated bristle bur. Easy as
pie… Took the residue of a years worth of high school kids
working my 13 files to death.
Let’s hear some more!!!
Terry