We tried it for about 3 weeks. But we only have one bathroom and it just got to be way too much of a hassle. My girlfriend found the info online and was "in charge" of the training. I'll ask her where she found the info. It was a gradual process but our kitties caught on pretty quick. Basically you start out with a bowl of litter beside the toilet. Gradually you pile newspaper under the bowl to bring it to the level of the toilet. Then you place the bowl of litter in the toilet bowl. Gradually you decrease the litter in the bowl until there is none. At that point you remove the bowl altogether. We couldn't get past the point where you totally take all of the litter out of the bowl. We just got very tired of litter all over our only bathroom. We were very busy at the time and just couldn't devote enough energy to the process. Given enough time I know it would have worked. We may try it again later but right now we're concentrating on the kittens that are on the way.
I forgot a very important part. Once you place the bowl in the toilet you need to work with them to teach them how to go with their feet on the toilet seat and not the bowl. Start with their two front feet on the seat and the back two in the bowl. Then each time place their feet on the seat to teach them. Like I said, it's a process. You need to BE there most of the time. For those of us who have to work to be able to buy our babies wonderful toys and cat trees, it's hard to be home enough to work with them.