As you can tell I don't do them very often! When I do them I find it difficult to get them really clean and smear free. I have a boatload of cleaning products but no vinegar (and I don't want to go to the shops). How can I achieve a good result? I was assuming that first I wash them with soapy water to get all the dirt off, but them how to I get them streak-free? Will windex or similar do it?