Good luck with the skull.. !!
I attempted this once with a bat skull I found on an adventure on the woods.. but sadly, I tried the boiling method. Stupidly, I used a coated pot.. after several hours of boiling, I had a sickly grey soupy teflon & rotten flesh mess, a still flesh-covered skull, and an apartment that reaked like a morgue, so I had to abandon it. Sad too, the bat skull was a cool find..
I did not know aobut the method you are doing, so best of luck! =)
Bats are difficult due to their small size. I have used maceration on them 3 times. 2 times were successful, but one of them the skull disarticulated. It can be hit or miss with small specimens.