I know this sounds a bit funny, but I have had an
excellant result with just such problem with product
called Island Girl.
Click on the web site below and read on the product.
Island Girl is principally sold to clean boat parts
and products such as gel coats; but it is also used on
rubber and plastic types, etc.
What I found, to my delight, was that once applied, if left
on too long, it will remove things such as glue or paint.
Or paint???
Yes, it will, and all the while cleaning and lubricating the rubber from whince the paint is removed, as well as
adding UV protection to the rubber. Your rubber looks great -- similar to Armoral. Now that's cool.
Click and read on product(s), i.e., Island Girl Pink; White
or whatever. One or the other is more aggressive for paint removal, but I just can't remember which. Seems I've used each with pretty good result, as long as it is just overspray.
Go here:
https://www.islandgirlproducts.com/
Best of luck and wished I would have seen this sooner.
Dennis.