Good first flush. Yes, I'd say you successfully worked something loose. Clay like stuff is normal, bad smell normal, smelly urine normal. What you're passing sounds normal; a zoological wonder I say, amazing what we have been carrying around isn't it?
I agree with Lisag re colon cleanse. Do an enema using warm water, or even better, coffee, but do one! Do take a kidney cleanse (except not the day of the cleanse). The first cleanse is the hardest, taxing as someone put it, the 3rd one is a breeze. Take vitamins and minerals and I understand that magnesium is good. Also, take yogurt or probiotics to help replenish the bacteria in the stomach.