Here is my sequence.
Take the tyres to a shop and see if their bead breaker will pop the tyre in. You may get lucky.
If that fails: If the tyres are very old and have RAYON written on them, the rayon can rot and the tyre may not be trustworthy. Consider junking them. Or: NYLON is better and newer.
Soaking- try gas but I think it would attack and damage the rubber and the rayon. All mine were wet in the bead and so oil wont get far- a night with coke is probably as good as it gets.
then- most of mine took all day with a crowbar to slowly work around and break the bead. They will break in the end.
Where the tyre is junk, you are lucky. Let the air out and cut around the sidewall as close to the bead as you can. Then use an angle grinder to cut the bead from within with a disc. The rubber will smoke and this isnt good for the disc- wear protection. Once the bead is broken they fall off.
Old tyres crack in the sidewall. The best thing I have found is 25% black show polish, 75% wax (candles), and enough turpentine to dissolve it into a slurry- takes a few days to dissolve. Paint it on thick and be amazed how it soaks in and dries hard. Old dried out tyres are more porous than you think.
I bought Chinese Linglong tyres, they look fine although i have not driven them yet. They must be better than the other 40 year old tyres I have.
good luck.
