Heard on here I believe you could possible take the dent out of an old Webley Oil tin with a bicycle pump? Was finally using an old tin in a casing and the dent really was bad. I have a car tire pump you plug into the car socket and it had a Presta valve screw on converter for bikes. That converter had a O ring that perfectly sealed on the tin top. Just holding it on in a flash it popped out. Not totally but a huge improvement. Plus it blessed me with a little squirt of red oil on my shirt.