I would never use 'goo' (not the lube to install a tyre) to attempt to repair or seal a leaking / faulty rim - tyre fitters nightmare apparantly.
There are wheel refurbishment places near me that say they can remove 'up and down' flat spots on alloy rims, as long as it is a gentle indentation rather than a severe crease. The weakest point of any wheel is the inside rim which is furthest away from the spokes (thats one reason why you shouldn't straddle individual speed humps too fast, especially with low profile tyres as this puts extra stress on the inside of the rim which is the weakest point...

). They use wheel straightening machines, which locate the defect in the rim, and then hydraulically remove the twist, flat spot or indentation returning the rim back to being perfectly true. This is normally done as part of the refurbishment process, but I'm sure it could be done purely to straighten a rim that didn't otherwise need any cosmetic repair.