Tried it and unfortunately it didn't work. I put on 4 coats and these came off just fine; however, the old stuff stayed put. I've invested about 6 hours scraping on the windshield so far and still have about a quarter size spot left to scrape. Haven't started on the front windscreen yet! I'm using an old plastic card hotel key that I sharpened the edges on to slowly scrape away this concrete! I'll be faced with polishing the plastic after I finish the scraping.
Ended up with a bit of crazing as well from pushing a little to hard on the plastic. I've tried iso alcohol, soapy water, vinegar, denatured alcohol, mineral spirits and Windex and the mask is un-fazed by any of it.

JC