I have done 16 flushes, and the last 6 or so I have eaten fats and protein (like chicken/liver/mung beans) and had a little coconut and olive oils at lunch time.
I always do an enema the morning on the flush and the day after.
I eat a large protein and oil lunch on the day of the flush at around 12 noon, then I eat no more until I do the flush. I take at the same time a tablespoon of lecithin granules plus some digestive enzymes.
I'm one of those people that get really depressed and irritable if I don't eat in the day, without oil, I feel very unsatsfied.
What I have found is that eating as above has produced better results - loads more stones!
Some say that eating/having undigested foods in the stomach will make you vomit, but I haven't found that to be the case. I always make sure I drink several cups of peppermint/ginger tea on the day and day after the flush.
I think people need to experiment to see what works for them rather than blindly following someone else's protocol.
The flushes I did without a good meal inside of me produced very little.