Not every clay would remove the over spray efficiently. It is expensive so you can't experiment. 3m cleaning clay however is for OEM use and is good for over spray removal hence I suggested that. It costs about 5k+ for its 200g bar. Given the grainy texture you are mentioning, it will pick a lot of contamination so I am guessing the bar will be fully loaded with contaminants.
How about you drop by to my house ( peshawar road, rwp) sometime this week (ideally Saturday morning if you can wait till then as weekdays routine is tight) and we can do a test spot to see if clay would be useful. I don't have the 3m clay but another one (riccardo yellow) but it should give an idea if clay would work or not. Even if it does half work, we can be sure a more aggressive clay would take it out fully. I hope it doesn't overload my clay bar
Share pictures from different angles first and wait to hear more expert opinion.
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