When I started flushing about a year ago 1/2 cup of oil did nothing for me. Then I used 1 cup, still nothing, then 1 1/4 cup that produced about 1/3 cup 'harvest'. For the last
several flushes I have been using 1 1/2 cup every time, result: rounded 1/2 cup debrie, with no liquid.
I am 67 and I think that my age probably has something to do with that. I take two tablespoons lemon juice and 3 tablesp. OO (Olive-Oil) every 15 minutes. This way the lemon juice is on the bottom of the glass and it is the last thing you taste. I don't mind that part any more. It is important to drink your cocktails down standing up. I have done 31 flushes so far. There is lots more where those stones came from.