[DaleHCook]

For something like your rusty transformer housing my preferred approach is a Dremel abrasive buff, They are plastic sponge wheels bearing one of three grits of abrasive. They are much less drastic than wire wheels.

On using a dimmer, I would discourage you from feeding anything but a pure sine wave into a chassis under test. Dimmer outputs are too jagged and noisy. My custom bench AC power supply uses a Variac (if it isn't GR it isn't a Variac) and a true isolation transformer. See:

https://plymouthcolony.net/starcity/radi...tml#variac

and

https://plymouthcolony.net/starcity/radi...tml#wp-26a