I would like to offer a suggetion about helo transparencies.
I can only speak with any credibility about Blackhawks but I am pretty sure that crewchiefs are the same everywhere.
I clean the windscreens and cockpit door windows before and after every mission. The canopies and chin bubbles do not get cleaned as frequently as long as visibility through them is acceptable. The gunners windows only get cleaned when it is cold outside and the cargo door windows are cleaned on an as needed basis. In my experience, this is a fairly common practice. The logic behind this is that the only glass we have is the windscreen, all other transparancies are plexiglass and the more that they are cleaned in a field environment the worse the scratches become. Even after being cleaned with window cleaner, there is a slight haze over the window. To get rid of this, I clean the window with pledge after the Windex, but this takes time that I don't always have. Now that we are back at home station I will have the time to polish them all on a regular basis.
If you are building a heavily weathered, desert aircraft don't worry about clear windows, clean ones often won't be crystal clear. The cargo door windows are often oil streaked and covered with sand. Just be sure to keep the windscreen and pilot door windows clear.
If you are modeling a Stateside aircraft, the windows should sparkle all around. If they don't, then you need to fire your crewchief.
Mac