I have done 4 flushes and eliminated over 1000 stones using cold pressed, extra virgin olive oil right off the supermarket shelf. From what I have seen, my results are typical. I am not aware of any advantages to using a special oil from a health food store. I would not be overly concerned about it. Several posters use olive oil that is extra light so that it is easier to drink and I assume easier to keep down.
I will continue to flush as long as I continue to get a lot of stones. Typically, I have noticed that people get more stones out on your second flush than the first, I think because the first one just starts to get the stones moving. So the sooner you get started, the better. The ultimate cleanse is not necessary to start liver flushing. I have not done it yet, but I plan on trying it.