The first time I washed my GTD with a hose, I spent the rest of the day drying the carpets out.
Since then, I have developed a system that works, even when it's filthy.
You will need one of those squirty bottles that fires a fine mist spray. Fill it with water, to which has been added a small amount of washing up liquid. It shouldn't be concentrated enough to foam.
Spray this on sections of the car at a time, starting with the windscreen and windows, working over the roof and down the doors. Then, before it has a chance to dry or run off, take a hand sponge and a bucket of clean water and wash the areas with it. This is what removes the dirt; the spray merely wets the surface.
Remove the front nostril, open the front and rear clips and wash in the same way in the open position. Don't get water into the plenum chamber, you'll be mopping it out for ages afterwards. White spirit or kerosene is very good for removing bugs and tar.
The front nostril is cleaned off the car, allowing the splitter to be cleaned properly. The wheels can be cleaned with a stiff wheel brush and hosed clean. Run the car after cleaning to dry out the brakes and discs.
Change the water in the bucket frequently. If you can see dirt in the water, it needs changing.
Once the car is clean, leather and polish.
Needless to say, do this out of direct sunlight and in as cool conditions as possible.
This method works very well if the car is really dirty. If it's not too bad, I just lick it clean.
Tony