I prepare skulls and skeletons for the science division here at Minot State, to degrease bones, soak them in hot (not boiling) water with dish washing detergent and some oxy-clean, small bird bones and such you can do in an hour or two, you may want to drill small holes in the ends of the bones to allow degreasing into the marrow cavity. Thats the degreasing part, then do another hot soak in peroxide/water as stated above for about the same time....Deer skulls usually take eight hours/eight hours, so gauge time accordingly. Most folks do not realize that degreasing and whitening are two different things. Whitening is easy if the bones are properly degreased, but the degreasing is the hard part...and if they do not degrease the first time, we think the fats get turned into what equates as soap, or the beginnings of it, and it gets locked into the bones, so further degreasing attempts tend to be futile at best....This is at least what I have found with an entire chemistry department at my disposal....Never use bleach, as it continues to break down the bone even after you think you have stopped the process (dry) and after a year or two the bones will be powder...seen it happen to lots of museum specimens done in bleach.
I went to Party city and bought a bag of bones for 10 dollars...it was basically a complete skeleton i na bag....the bones are like a plastic but look very real. they worked for me...or u can continue with the method ur doing with the real bones