Great advice, our beloved Capris and buggers for dirt traps, mine wasn't too bad but the usual front wing traps were in need of some new metal.
They certainly are! Mine had shit loads in the rear arches when I first got it, all impacted in up under the sill ends and spring mounts.
The fronts had it all flung up to the fronts of the inner wings. It had all stuck to the backs of the headlight bowls, probably why mine were so rusted. I've got a pair of the aftermarket metal splash shields for the fronts now though. Should stop the A post bottoms and heel boards rotting out again. Hopefully.
To be fair the Smart Roadster manual says that you should never use a car wash or pressure washer on it, as it'll damage the seals. Quite a few people have confirmed that are true!
Pressure washers are great though for getting crap out from behind trim and hard to reach places. Just have to use it with precision.
A pressure washer can be good but as you say, you've got to be careful to not spray it at windows or seams on full power as it will blast water in, especially so on old cars where the joins and seals are not as good as they once were.
Also, if your cars a bit rusty don't use it! It will literally blow the rust, paint and filler off if it's bad enough!
I used one on my Volvo 740 when I first got that to get rid of the years worth of grime and algae that was covering it. Worked a treat but I avoided anywhere that it could cause trouble and did that by hand. Old Volvo's are hard though so no need to worry!