I've just finished getting about 95% of the mud off the bottom of the
pinz using one of those blunt cross-head screwdrivers specially
engineered not to fit any screws, plus my fingers, and finally the
blast gun attached to my compressor.  The mud was all dry so was happy
to come off and the blast gun worked quite well, prodding the big
chunks of mud with the probe without any air tends to make them crack
up and drop off, with the occasional blast of air to keep the probe
clean, then using the air blast to clean out the nooks and crannies.

The advantage of all this is that I now have a driveway covered in dry
mud that's easy to remove with just a broom.  Eye protection is
essential when using the blast gun!  It's a lot less messy than water,
and means you can get under the truck on a car crawler with the air
gun and clean off the bolt heads and joints using the air, instead of
getting wet and grubby you just get covered in a light coating of
dust.  I doubt it would work well on wet mud though.

Now I'll take the pressure washer to it to hose off the small amount
of remaining muck, which won't leave much mess on the driveway.

I've air-blasted so many previously un-cleaned nooks and crannies that
I'll probably go down with some disease that's been dormant in the
swiss mud for so long mankind has evolved away any defence against
it so if a sudden plague sweeps the country, sorry about that chaps.

I have a K299[*], detergent bottle sits behind the handle. It always
struck me that a stand alone detergent bottle would just ask for being
kicked over and/or make moving the machine a PITA.

I reckon mine is about 3 or 4 years old but it's probably only been used 2
or 3 times. The rain does a good enough job most of the time, though it
doesn't shift the algae.

[*] I think, just been to check the model but I can't actually find it
ATM. SWMBO'd has "tidied" the room it was last seen in... K299 on the
karcher website doesn't match what I have but I guess "fashion" has
insisted a redesign of the plastic covers.