There are numerous resources for cat toilet training. They have several books written that give step by step instructions. YouTube has a number of videos on how to train your feline. If you are planning on keeping the cat in the house and hate the nasty litter box, this is a project you may want to look into. The results usually depend on their personality. We all know that each cat has its own personality and likes and dislikes, but a few weeks is usually how long the process takes.
The process is a series of steps that move the cat to the toilet. So each step is done and then let them adjusts to that part of the process. How quickly they adjust depends on the cat. If you see set-backs like the cat pee on the floor you may have to back up a step and try again in a few days. Any cat who wants your approval will do great at this.
Flushing seems to be a problem with cat toilet training. They can be trained to flush by attaching a weighted cord to the toilet handle. This doesn't always work out the greatest as the cat usually doesn't understand why they are flushing and will do it just for fun. So you may have to just make sure you stroll by the bathroom and flush the toilet periodically. If that concept really bothers you may have to go back to the cat box.
Cat toilet training multiple cats may also be a problem as the cats may not all work at the same speed in the steps. It is also hard to figure out which cat is not adjusting. You have to be able to keep tabs on all the cats so you who is doing what although it can be done, it just maybe more difficult. If cat toilet training is something you think you would like to try, check out a book or look up the video's and get started. It has been done for years and there is a lot of material available to help you get started.