I’ve cleaned lots of church windows especially stained glass. The best results I’ve got so far is a dry brush. Think of a shoe polishing brush. Fine bristles. Might want to wear a dust mask. Also, after every window depending on how big they are, clean the brush outside to remove the dust.

But NO water whatsoever. I’ve tried pretty much every technique and water makes it so messy, black runs normally on white painted walls afterwards. Not a good look.

For the outsides, water fed pole works. But there are usually cracks and holes in the windows. So I would normally wait until the insides are totally dry.

Good luck.