I tried multiple methods and tools, but nothing seemed to work well. I found that my fingers were the most efffective tool, but unfortunately they were wearing out quickly and I only had so many.
So I started thinking, what other object might I have that has similar properties to my skin?
After a short search I found a chunk of rubber left over from an old project. I cut it down to a size that was easily held and applied it to the task. Just press and rub anywhere there is sealant.
Worked very well. Finished cleaning two tires in about 20 minutes.
HTH
I’ve had good success with (gasp) high pressure washers. They just take the old sealant right off and as long as you remove the tire from the bike before doing it, all your seals and bearings will stay intact.