[morzh]

1. You cannot solder to the can as it is aluminum. It cannot be soldered to.
2. Yes you could take a tinned copper strip and rivet it to the case, and then solder to it. Some caps were this way so it would ne authentic, but a rivet is only so much reliable and may potentially oxydise over time.
3. Using two wires you don't have to isolate the can from the chassis.

Any way you could output two wires is fine. I go for the simplest one.