FWIW, eucalyptus oil can be applied to paper products (to remove old price stickers, for example) and once it evaporates, there is NO trace of any stain whatsoever.
I've done this hundreds of times on expensive booklets ($10 for an 8 page one) and there has been no damage from staining. The only time I have any hassles is if the booklet is printed with an ink that the eucalyptus softens - a rub will smear the ink. A very special technique is necessary for these ones - but you won't have any hassles like that with component leads.