Brake cleaner or carb cleaner works pretty good for cleaning the EGR valve and EGR passages in the head and intake. You'll need to use a stiff wire, or a broken speedo cable to run through the passages to break up the build up.
You can use a small screwdriver, to scrape the sides of the holes in the EGR valve.
You can use a small drill bit to clean out the little tube on the top of the EGR valve. Just start with a small one and keep going bigger until you get the build up cleaned out with out actually drilling into the sides.