A few frosts & coming winter weather might help things along, weather too cold to paint it at this time of year, leave until the spring.
Why would anyone....apply a substance ...to anything....without first reading the date sheets from the manufacturers of said product ? It's not rocket science. Just go into bNq and ask one of the girls ....they would have more idea..... To quote my hero Victor Meldrew....." I doooont belive it " RS
Okay, so it was a mistake. But without experimentation we don’t discover new things. The OP also published a negative result, so we all know what not to try. If it had worked then the OP would be internet famous with a YouTube “shed hacks” channel. But on the subject of how to get it off - I have no idea. Time? Surely UV will break it down. Now, you’ll have to excuse me. I’m going to see if cheese strings can be used instead of twin and earth.