Just as long as your are sensible you will be ok, if you are worried about certain things cover them with a plastic shopping bag or tin foil moulds well, if pressure washing turn down the pressure if you can & stand back a rinse is better then trying to blast dirt off, I would start with a cold engine, rinse, spray on your cleaner, agitate with a brush in all nooks & crannies leave to dwell for a few minutes & then rinse off, dry off what you can with old cloths & then you could start the engine & let run for a while to help dry out a bit more, once dry off with the engine & apply dressing, gently wipe off any excees dressing job done, lovely !
Barry