I searched around long and hard on the tricycle forums and the only thing that I found was a suggestion to put the solid tire in boiling water to soften it up. I have a schwinn lil' bandit that needs a rear tire replace. I now have the tire, but i have not attempted getting it mounted yet. I was thinking of suspending the tire in the water with strings to keep it off the bottom of the pan while being heated????
This is just my own idea, but I was also thinking of slathering the wheel up with vasoline or something like that to help things slip. a co-worker suggested dish soap, but I hesitate to trap any water based anything under the tire against the metal.
They did mention wearing gloves.
When you find the successful tire mount process, please PM me how to do it, or hopefully not to report how not to do it.