Hi trippyboy, from my experience on insides i would always use a damp microcleaning pad just with water to deep clean and remove any residues left on the glass from additives like wash up liquids or traditional glass/mirror cleaners, then i would detail with a damp good quality microfiber cloth just with water and finally polish off with a dry good quality microfiber to achieve a perfect smear free finish, i find this method to be very effective and you won't have to worry about the sun showing up any residues.
I took over cleaning a shop from a windie who had, sadly, hit the booze big time. He had cleaned the shop windows for years upon years upon years with good old fairy. As it was/is easier and quicker to do the place wfp I used/use that. 8 weeks on and the bubbles are still coming off the glass but nothing like they were to start with. The 1st week it was windy and the bubbles coming off blew away in the wind.
Detergent contains glycerol or glycerine and also usually silicone. Both of which will leave smears. It's a fact. Look at any window cleaned with detergent in low sunlight and it will be all smears.
Inside glass doesn't tend to be cleaned as often as the outside but the same principle applies although to a much lesser degree.
