This magazine always has something interesting. Look at what they suggest as dye solutions.
http://books.google.com/books?id=TyQDAAAAMBAJ&lpg=PA122&dq=drill%20sharpen&hl=pt-PT&pg=PA144#v=onepage&q=drill%20sharpen&f=true
http://books.google.com/books?id=TyQDAAAAMBAJ&lpg=PA122&dq=drill%20sharpen&hl=pt-PT&pg=PA144#v=onepage&q=drill%20sharpen&f=true
