I have 2 cats. I purchased the Fresh Step Scoop Free Litter box. I am not able to get them to use the automatic litter box. The pamphlet tells you to leave te used litter box next to the new automatic litter box. Well, it smells gross after a few days... And, one cat will urinate elsewhere... while the other just goes in the dirty litter box. Please, help with any ideas. Thanks - much appreciated.

Im wondering if you HAVE to use Fresh Step crystals for the ScoopFree automatic litter box or if you can use a different (less expensive) brand of cystals?