I've done three skull mounts, thus I'm no expert, but every time, I soaked the skulls in acetone for 24 hours as an intermediate step between boiling and applying the peroxide/bleach paste. No oil what so ever, the skulls are pure white and have a nice "shine" to them. Very nice presentation. I'll have to wait for a couple more years to see if any smell shows up but...

One extra precaution I dreamed up was to spray a polyurathane into the brain cavity and nasal cavity. You can't see it is there and in my mind, it seals in the inner parts that I might have missed but can't tell.

Greg