I like to whiten with Salon Care 40 Volume Crme, but don't brush it on.
I boil a fresh pot of water and dump the bottle into the water. It distributes the peroxide evenly and throughout each nook and cranny of the skull. I let the skull soak for about 15-20 min. Rinse with clean water once it comes out of the peroxide. And then you're good to go.
The bottom skull was whitened, the top was not. It's your call. Either way, great deer.