I know nothing about litter box training, but I can give you a link from YT, where they talk about stain and urine remover. I just used this recipe and it really does work. Good Luck and Welcome!
http://www.yorkietalk.com/forums/yor...-recipe-2.html http://www.yorkietalk.com/forums/yor...-recipe-3.html
Make sure you scroll down for the recipe and read what others have to say.