[blaustrom]

You got all the correct answers. I would add. The tire needs to be as hot as possible to make it more pliable, especially for a very stiff one. Also helps to use C clamps and 2x4 pieces and force the beads together to soften up the stiffness a little.
There are numerus threads here about tire changing, what lube to use, what mounting bars if you use a changing machine.
A cold stiff tire without lubricant is the kiss of death. Put a hot air source inside the tire before mounting, better still a sunny hot day and put the tire into the sun for a while.

Conditioning of a Dunlop Trailmax, also fairly stiff:

 

[blaustrom]

Not sure what detailing spray is but some of that stuff is corrosive for Al rims. Get proper tire mounting lube, you need only small amounts each time and it makes a huge difference, also seats the tire easier.

 

[blaustrom]

The coatings in the past were probably not as good as powder coating nowadays. If I look at my 2007 KLR rim, that had really no coating on the inside.
Fighting with tire irons often leaves nasty scratches in the powder coating of the rim, a good start for ongoing corrosion and ultimately a rim leak, if not cleaned up.