yup, the flush can still work. there aren't always stones on the first try, so if you don't get stones it isn't necessarily from throwing up. i've thrown up immediatly after drinking the mixture, and hours later, and still got stones out each time.
i cut down on the epsoms salts by 1/2 or more, and have stopped throwing up ever since. i've had much more pleasant flushes with less epsoms.
some people take peppermints after taking the mixture to cut down the nausea, i've heard good reports about that. others have taken alkaseltzer gold or ginger for the nausea.