Lots of sound advice in here Kev.
If you keep up with regular washing it's easier to manage.
Snow foam and pressure wash first (gently, not full blast) to get as much grit off as possible before you touch the car.
Two buckets, dip in the shampoo bucket, start at the top (cleanest) and work to the bottom (dirtiest). Constantly go back to the clean water bucket to rinse the mit and keep as much grit off it as possible then back to the shampoo bucket and carry on.
Two towels is a real big help. Really careful drying, it's a point where it's really easy to drag a bit of grit right across your car.
Keep everything as clean and free of grit as possible. If anything touches the floor it's game over
If you do that, and then hit it with some PB Black Hole and then give it a coat of Zaino Clear Seal your car will look like it's made of glass.