Whilst it's true what others have said, this does mean you can charge a premium for this service.
First thing you have to find out is internally are there ant coatings on the glass, this could be film or some other type of coating, you need to find out exactly, contact the manufacturer if you cant get written confirmation form the site manager, if the information is there, follow it exactly!
Last thing you want to do is bugger up the glass

How bad is it, look closely at each and every pane, is plaster paint splattered all over the place?
Price between £3.00 and £10 per pane, depending on answere to above!
Regards,
Rob