I've cut old tires off and I've remounted two tires on my 2-piece rims. It was a chore and it took two of us with prybars, a 20-lb maul and what not. After the second one, we noticed the tube was in backwards (valve pointed the wrong way) ... That's when I said "enough of that" and found a tire shop to do it for $15 a tire.
We have a truck tire place here in our small town. The owner is in his 30's and no stranger to multi-piece rims. In fact all of the guys in the truck club here get their tires done there.
Any place that does truck tires or ag tires should know how to deal with multi-piece rims. And they don't even have to be old guys to know what they're doing. Funny thing, speaking of old guys, I once tried the old timer in town (in his 60's) -- he took one look at my 2-piece rims (NOT the Firestone RH-5's) and essentially told me to get lost. The 30-year old guy took them in and did all six while I stood there and watched.
All the home tricks and old guy techniques still can't compare to the ease of giving a guy $15/wheel to do it

John