Jay and all,

Without question the best stuff I've found for cleaning airplanes is
Tomar TR-1000. It is designed to be safe for aluminum airplanes,
unlike the cleaning products you'll find in your local discount store.
It is extremely effective when diluted and used as directed.

Unfortunately it is expensive and not easy to find. I ordered a 5
gallon drum of it directly from the supplier, which added on shipping
costs. But it lasts a long time.

I wash my plane 2 or 3 times a year. I'm in a generally warm and dry
climate from April through October so I'm not worried about corrosion
that much. The wash rack at my airport has very hard water, so my
trick is to take a high-quality silicone rubber squeege, 1 to 2
gallons of distilled water, and a garden sprayer. After washing with
the TR-1000 (diluting as directed) and rinsing with the hose at the
wash rack, I squeege off the hard rinse water wherever possible. Then
I spray important areas like the plexiglass, or curved shapes I
couldn't squeege too well, with the distilled water--enough to make it
run off, displacing the hard water with distilled water. I towel dry
the other areas that I squeeged but didn't spray. Finally I'll fly it
around the pattern to air dry the crevices.