Dash-T, I take it you are looking for a tip on which chemical to use or some trick of the WC trade. There are loads of blokes on here with as many ideas about internal cleaning as there are windows to clean. I'm trad and that's inside and out. Can't see a problem but, you don't have the experience to do that so, I would say use what you use at home. Whatever it is. There isn't a secret to it. Unless you want to buy a WFP system (for inside, abit overkill IMO) or do what I do, mop and squeegy.