I just installed my window AC unit and then opened it up to discover that the cooling fins have quite a bit of dust caked on it. The dust looks sort of like papier mache and is sticking to the fins (a vacuum isn't pulling most of the dust off). I think this happened last year when I wasn't able to clean the filter soon enough and a lot of dust got through and got stuck to the condensation on the fins.
How can I clean this without removing my AC unit? Because of some undesirable features of the windows in my apartment, taking out and putting back in the AC unit is quite a laborious and time-consuming process. I've used foam cleaner before, but only when the AC units weren't installed so that I could hose them down. Are there foam cleaners I can use on an installed unit without making a mess?