Ahh yes, the bane of my car cleaning routine, I've put many pennies in the swear jar because of this. When I first got my car it was horrendous and I resorted to using an air line as I could get the nozzle fairly close to it. I also used a piece of thin metal to work free some of the tougher to reach areas. Now that the car gets cleaned on the regular, blasting it with the pressure washer usually does a decent job, but maybe for a first time, I would recommend an air line. There is also fairly decent access from the wheel arch once you remove the cover (if you can be bothered to do that) and full lock the wheels to improve access. Once you get on top of it, just becomes part of the routine!