Thinning epoxy with denatured alcohol is better when you wish to slow the cure so a heated epoxy ( which speeds the reaction) can cause it to wet out fiberglass or other composites. Acetone is far faster on its evaporating ...
Just an FYI...
you can also thin Goop with acetone and clean it up on something as long as you are not getting it near what you are trying to glue as it will wick under/into the glue joint edges causing it to lift and break the bond. Another chemical good for thinning Goop like adhesives, Goop or Shoe Goo, is Xylol. I like to use Xylol, it seems to thin the Goop better. The thinning will slow Goop's curing some, but its a fast curing/skinning , adhesive.
Not that you would ever wish to consider Goop for this wheel leak.
Most silicone adhesives have that characteristic acetic acid and Goop being a silicone compound has it as well. I would not risk thinning a silicone you were trying to seal a rim, in case you decide to go that route instead of going with epoxy.