Soda blasting will inpart a shine to the case as the soda is so fine, glass bead really opens the surface, and will inpart a dull finish, that will soon oxidize, find someone that can blast with walnut shells or cherry pits (really) it will inpart a more natural finish, you can easily block the side tubes with npt plugs, and tailshaft slip in plugs are cheap, from Summit, Jegs, etc, keep or throw a converter in it to prevent anything getting past the seal,make a strap/bolted across the converter to hold it in, and either remove and plug the tube hole, or duct tape the handle in the tube, plug the vent with a npt plug,...then you should be good to go, have them stand it on the bell only when blasting