More than a few posts regarding hull, deck and interior cleaning, mention my all time fave; TSP and bleach.
At the level of filth seen in this post, I'd start with a garden hose nozzle - full pressure - and see what water alone can drop. Any small utility pump (Simer, bilge, even a siphon) will remove most of what gets into the bilge - or the cabin - probably both.
Savorin, among others, makes TSP (available at HD or Lowe's or ACE) which is ~ $5.00 a pound and a is a non-sudsing detergent with incredible cleaning power. Extremely alkali but no where near lye/Draino. Of itself it is extremely anti-bacterial but with a splash of bleach, would kill mold from a block away
I'd hose it down until what water alone can't remove - is all that's left on the surface. Soft car-cleaning brush on the gallon of warm water + 1 cup of TSP + 1/2 cup of bleach and watch the filth run down the surface(s).
Rinse with hose spray and let the bilge/cabin pump run wild.
The stuff leaves no "soap" slime and despite it's cleaning power, rinses easily.
Air dry for a day or two an voila - dirt gone!
Of course everything not nailed down or painted surface, should be removed - but you already knew that
So we have the before pics. Let's see some "during" and "after" shots, S.V.P.