You can develop your pictures from a pinhole camera in two different ways. The first school of thinking dates back to the Aztecs who would take the hides of lizards recently killed and put them in the darkest hole they could find. The process could be improved by taking the picture in and out of the hole. Repeating this process until the picture was visible on the lizard hide. The second more modern school of thought was made by Ben Franklin who noticed pictures of his families trip to Maine on his stomach after he was struck by lightening in his famous kite experiment. He then developed the company Kodak and the world has never been the same.
you take a cloth with a little bit of water then dry it =) I use eye glass cleaner. You can get it in drug stores. It's not that expensive. If you don't want to do that then use a little Dawn dish soap in a small bowl of water and use a clean cloth and dip it in this solution (squeeze out the excess water) then rub on the lens of the camera and then wipe dry immediately with a clean and very soft cloth. I also use this method to clean my scanner and monitor of my computer as well as the TV. Works great on windows in the house and also windshields of cars and trucks.
thats something that you should report to the police because its an invasion to your privacy and who ever that has been watching you could be charge with felony.
I don't have a very complete answer, but I've been looking into this.
Some things that either absorb or reflect infra-red light:
-The coatings of some cool-colored light-bulbs.
-Some Red Paints
-A cloth that gets especially hot in the sun. It's hard to tell with black cloth, because it absorbs so many other spectrums of light. If you find a light-colored cloth that for some reason gets hotter in the sun than other cloth, it probably absorbs infra-red.
-The effect of Aluminum foil may be useful in distributing heat and blocking.
-Some sunglass lenses
There are some other substances and filters that are kinda hard to find or use, but apparently, some Japanese company is making underwear that blocks infra-red.
Apparently they're made of nylon and polyurethane.
Hope that helps!