Not sure nail polish was used to seal the primer, seems the reloader? pushing the nail polish thought it was good stuff to hold primers in primer pockets that were loose.
Then there is the cleaning part, I have no clue if the part to be cleaned is coming from the inside out or if what ever it is that is bothering you is just on the outside. If I was concerned I would pull a few cases down and examine the components, if the primer pocket is clean, the primer is clean and if the powder is not caked up I would apply the ‘Leaver policy’, I would leaver the way I founder. And, If I was concerned about leaking primers as in the exchange between the atmosphere in the inside of the case with the atmospheres outside the case, I would do an atmospheric exchange test, because, I am the only reloaders that can preform a vacuum test without a 100% (perfect) vacuum, I could do a pressure/release test, most dangerous unless a pressure container is not available, anyhow a vacuum test is the safest of the two methods.
I do not know if the ammo you purchases is new/old stock or if someone reloaded the ammo and sold it to you, a lot of that stuff goes on when there is a demand and no supply. Next time purchase two boxes then take one to the range and determine if they fire. If there is a reason for the mess on the outside coming from the inside painting the case head will not stop the problem.
F. Guffey