Agreed, let it soak in a vinegar/water solution for a bit, and it should wash out much easier

You can pour some white vinegar, undiluted, into the bottom and particularly on the hard-to-clean areas in the pan. The take some plain baking soda and sprinkle it on the vinegar. It fizzes for a minute. Let it soak for another minute or so. Scrub the area next with a cloth (paper towels shred) and you'll find that the tough spots will start to come up. Then rinse the whole thing out and keep rinsing until all soda and vinegar residue is completely gone. Do this each time and your litter pan will soon be almost like new. If you get a new one, do this lightly each time and it won't get the build up in the first place.

thanks it really helped i should of taken before and after photos