I always eat fat on flush day...I had really disappointing results when eating lots of raw fruits, vegs & juices prior to the flush...& my worst flush, I ate watermelon...my theory(unsubstantiated) is that I was eating such a low fat diet(unintentionally...), that my bile making was in "sleep" mode. If anything, I would suggest not eating such a heavy(as in, hard to digest) meal on flush day,as it's going to be expelled not too much later.
Everybody's different!