If your doing a church and it includes the stained windows make sure you are fully insured because these things cost tens of thousands to repair.
You will not be allowed to use any chemical on them either and check with the warden regarding condition etc...
We used a sponge with flexible clamp for high stuff then microfiber cloths to dry
You might also find that there are lots of metal support bars with ties that catch on the cloths etc...
Make sure it's a good price.
Darran
Ps - hot steam may damage the lead work, or crack the glass you would need to find out if this was an approved cleaning method