Shaving a tire is not so hard and maybe not even necessary for a tread swap. When I made my home made tire casing I was able to peel the tread rubber of the casing of my donor tire. Doing the same on the casing you are gluing to would both remove more weight and be much faster than shaving the tire.
So peel, peel, glue, should not be too difficult. I am going to give it a try once/if I get my 19 back from my friend in Montreal.