All of these are good but reading them a couple of thoughts come to mind. Never wash a hot engine, you can damage it.
The other is combing the suggestions already given. Blowing air will move most anything not stuck but not always easy to direct or steer it where you want it to go in a tight area such as a cab. Vacuuming nozzles have to normally touch it to get the dust and dirt. If you have a shop vac, take the suction hose into the cab and leaf blower or air hose and with vac running blow the dust and dirt to be moving. Vac should find it easy to pull the air with the dust and dirt and no fine steering with the pressured air is required.
Let me add here: I had a brick wall in our first house we wanted to cut through to install a door. Room had carpet and furniture in it. Fortunate where I was going to install the door already had a smaller hole for a firewood box. I took a 3 or 4 foot shop floor vac and set it in my garage and boxed around the fan. It was far enough away the brick dust fell before reaching the fan but we had almost NO dust in our house.