I dont seal my bones with anything. They are usually perfectly fine without any “sealing” as long as they are properly cleaned.
The only situation I have heard of where someone might need to seal bones is if they are so old they are falling apart or if they have been cleaned with bleach and are flaking.
The only thing I’ve had to seal was an armadillo pelvis that had been in the blazing sun for long enough to make it fragile, and I dipped that in a clear acrylic that’s meant for casting.
Bones that aren’t actively falling apart are pretty sturdy. Heck, I have a catfish skull that still has a lot of tendons on it (because it would fall apart if I removed those) and it hasn’t needed sealing. Bones with nothing more than a few scraps of dried tendon aren’t very hospitable environments for any sort of pathogen, if that’s your worry. They don’t have any more germs on them than the rest of the things in your house.