Don't know about the re-boiling, but you could try soaking the skull for a day or two, might rehydrate the flesh and make it easier to clean off.
As for whitening, with mine i got a 1L bottle of 50% peroxide off trademe for $20 and poured that into a container with water till is covered the skull and let it bubble away, think it was 12-14L of water in there
When it stopped i hung it up in the sun for a few days and it slowly whitened up, it didn't come out gleaming but was a vast improvement on before.
you could always use more or higher % peroxide or even simply tape up the antlers and spray it with flat white spray paint.
Hope this helps
Bookmarks