How often do you wash your plane?

Not often at all. Planes are for flying, not for washing.
However when take-offs begin to take 150m rather than 100 I will make a note-to-self to clean the mud off the wheel fairings, and perhaps the bugs from the wings.

I wash the mud & flies off after every flight using just water and a sponge/bug shifter sponge and then just wipe it down with a synthetic chamois. I use All-Kleer on the plexiglass. Takes about 10 minutes total as everyone else who flies the aircraft does the same, so it never gets really dirty. At least twice a year the aircraft is thoroughly cleaned (including underneath) and then waxed using Flitz Speed Waxx. Very easy to use, highly recommended product.

If the pilot washes leading edges after flight he is glider ( laminar profiles ) pilot as well. And if someone is washing the belly, he must be the one who has already or soon will experience what happens for transponder antenna hit by broom!

I use Liqui Moly Window Cleaener only. And Liqui Moly Speed Wax for Cleaning and Polishing.
Other than that I regularly wash and polish the airplane. Not because it’s necessary, but because I like the work and because I like shiny airplanes.

Impressive work.

In case you need another plane to practice your skills on, my plane is in the hangar next to yours

I know exactly where it is ;-) How about doing it together? With “speed Wax” the whole plane (without belly…) takes about 45 minutes.