I understand your fear of flushing, I´ve been there and I know what it feels like. However, 99% of the people who do their Liver Flushes got wonderful results and then we realize it is worth flushing.
The risk of a stone getting stuck is very low. I, myself did 16 flushes and never had a problem. IF a stone gets stuck you can take Epsom Salt and flush again, but if I were you I would not worry about it. Guess, fear is probably your number One enemy at this point.
About the anmount of Olive-Oil start with half cup and use grapefruit juice which tastes better than lemon. Use a straw to suck the mixture straight into your throat.
I agree with Hanna, read Mrs Chang website and you´ll feel more relaxed about flushing.
Remember herbal Liver Cleansing is good but nothing beats the effects of liver flushes.
Good luck and feel free to write more if you have fuirther questions.