I've found it more and more difficult to face the olive oil as I've done more flushes (I'm now up to about number 12). I found that grapefruit juice is definitely better than lemon juice, and pink grapefruit juice is better than either. These days I take about 1/4 litre of olive oil mixed up with about the same of pink grapefruit juice (I think 1/4 litre is about one cup, but I don't really understand the cup system of measurement). Once I've got that down, I then reward myself with another 1/4 litre of pink grapefruit juice which helps to take the oily taste away. The flush seems just as successful this way. If I feel queasy after getting this lot down I suck on really strong mints until I feel better.
Good luck with it