LOTS of people have very successfully done his flush. Andreas is a wonderful holistic healer that truly believes in TOTAL health, mind/body/spirit.
Almost all flushes share similar ideas, his includes 'softening' the stones first. However, his book is worth getting for the flush AND all the other information. Andreas has a wealth of knowledge that he shares.
Personally, I love Andreas, but do a modified Clark flush (although I got the idea of using apple juice / malic acid from Andreas) mainly because, deep down, I'm still pretty much a lackadaisical bohemian (fancy way for saying too lazy, lol.)
To more directly answer your question. I've done both successfully. It more boils down to your own individual condition and preferences.