IMO.....you are wasting your time and $ trying any stabilizing procedure on this burl. HRB is a true rosewood and does not need to be stabilized.
Definitely needs to be dry and cored tho. As far as whether it's dry or not is a whole different ball game. Legal burls have been illegal to hunt and acquire since around the late 80's if I remember correctly. So if you know your source they should be relatively dry. That being said, "dry" is a relative term. They could still carry a MC of as high as 15-20% depending how long they have been cut into usable pieces for cues.
My suggestion would be turn it round to about 1.375...blow a small hole (.say .650ish) thru it and leave it sit around your shop for a minimum of a 1-2 years. Weigh it after it's turned round and you've poked a hole in it. Weigh it again after 6 month and a year...see where it's headed.
If it comes with any wax on....scrap the wax off and leave it sit somewhere that air can circulate around it for a few years before you even start the aforementioned hole poking procedure.
Time times listed above are bare minimums. Joey is correct and if the above isn't followed you'll have a good chance of shrinkage after the build is complete.
It's a beautiful thing when properly done.
Big burl heaven !