i wouldn't be surprised if the mr muscle stuff has some sort of rainX or hydrophobic particulate in it as the screen dries really quick and smears like I've seen rainx do in the past. I'm not a great fan tbh as i don't like the way it can be a bit hazy with the wipers.
i did wonder if you could clay the screen... dont see why not.... ill look into some of that other stuff asap as you could literally see s**t all the other day. the damp roads were getting alot of spray and the low sun + smearing = no vision at all. i could barely see the end of the bonnet