lot of work, and I haven’t yet tried it, but I saw a segment on some outdoor show where they took the front window out from inside the bed byremoving the screws (without damaging so you can reinstall.) Then clean both and rain x to help them clean off on their own for longer and re install the window. Not sure if it works on all toppers and can’t recall what brand the one was they demonstrated with.
I thought about trying it on mine this spring but ran out of time the day I planned to do it and haven’t bothered to try since. I would think you wouldn’t want to be doing that method too often for fear of stripping out the screw holes.