Yup, one of the fun and zen things of 'performance' cycling in decades past.
While watching 'Chasing Lance' Last nite on Disco channel, I was surprised to learn that Team Disco still rode Sewups in the Tour. There was a short visit to the 'sewup cellar' showing the 'curing' batches of tahrs. I thought that for sure clinchers had superceded tubulars for almost everything.
Fond remembrances of finding just the perfect spot in my cellar in which to cure my tahrs.
Tubulars were never used until they were well cured at least 3 to 4 years.
I still enjoy riding them (since prolly 8 of my 12 wheel sets are for sewups) and happily have a bunch still aging nicely in a closet under nice moderating temps. Sadly, there are no longer any setas in my dwindling stock
But back to mounting. Just one of this apprentice things we all learned, and fouled up often enough. Was always a gas to check out competitors glue jobs and have a chuckle. Each big race (and most smaller ones) had a 'bike check' before okaying a rider for the start. First step was the 'twist the bars' trick to try and move the bars and stem in the headset. The dreaded one however was always the burly guy with POPEYE arms whoz sole job was to grab the wheel from the side, put his thumbs on the tahr sidewall and push with all his might to 'roll' the tahr off the rim - the casualty rate in 'Bike check' for the Cat 4 field was always enormous! Ah, fond memories. But this was the best thing cause even worse was the carnage to a field caused by a rider who rolls his tahr in mid-turn - better to not even let those start.
As for getting the glue off the sidewalls - I prolly wouldn't try, it is a futile thing.
For your future consideration, I found success in 1st putting the tahrs onto a clean rim and blowing up to full pressure one week prior to mounting and then stretching the crap out of each one just before mounting. Some guys used to have good success by partially inflating the tahr and slowly rolling it onto the rim from the side, keeping the orientation so that when it rolled on a minimum of adjustment was needed.
I prefer the uninflated method. I would put it on halfway, then use some small wood clamps with broad jaws to keep it from retreating off the rim while I yanked on the tahr to get the remainder on without smearing with glue... Hard to describe, you have to be there... the clamps have long since disappeared, but the technique hasn't let me down, since I mounted a pair, without much issue back in June.
Re your tahrs, The glue will dry, the tahrs will be ugly, but they'll still ride fine, prolly more than fine. Tubular ride quality is still a thing of beauty, if your bike is so equipped.