Like you I also have trouble with oil. I have done5 flushes with OO (Olive-Oil) and the last one was in May. I still smell olive oil everytime I defecate.
I started chanca piedra while I was also taking a beta food (Standard products) and using a colosan cheapie called "Super Colon cleanse" After two weeks of all of this I started passing stones in normal BM's. In fact i passed a couple of monsters this way. All in all I wouls say I passed around 100 or so stones and they were larger than what I had passed during an oil flush. What is odd as that many were elongated on discharge and very apparent to the eye. They were also extremely soft.
Now when I do a flush i never take the olive oil. I take the Epsom Salts at 6 and 8 and that is it. I still pass stones using this method although not as many as when i used the olive oil.
I backed off everything recently to give my bod a break. I stayed off of everything for a month. I will resume chanca piedra soon. I still believe my liver is loaded and I have passed a total of around 700 stones year to date.