Hey, OP Again!
Thanks all for your suggestions! I KNOW the replacement suggestion is
probably the best and most long-lasting of all, and I will keep the
instructions handy in my gmail folder. But this IS a 1970's era
fiberglass tub and I am afraid if Imess around too much, I may
inadvertently crack/stress the fiberglass.
And, since I already had to pull out one other showerstall from that
era in the second bathroom because of that very problem (cracked
fiberglass) about 9 months ago, not ready to chance that quite yet.
Anyway, I put a generous amount of Duralube Silicone spray on it
yesterday, worked the diverter back and forth several times and
finally left it in the "pushed in" position for about six hours. It
now works very smoothly for the time being. Time will tell.
And, yes, the mineral magic does work very slowly, but I am using it
on a toilet that has had "disgusting" hard water deposits for the past
15 years that we tried to remove with any number of items -- with no
luck. So, far, using the Mineral Magic since about May, I have
managed to get about 75 percent of the deposits off. Once a week
treatment. I figure I will go through the entire gallon about the time
it all goes away!