Dan,
I have limited success. I now bake into my bids extra for another trip out, as I usually have to do two trips for cat urine. I manage expectations with clients by letting them know that cat urine is far more concentrated than dog and that while I will improve it, I can not guarantee that I can remove it. I also let them know that I will make another trip out, if required, after a few days, hence my incresed bid. If you come across something that works, please let me know. Good luck.