magnesium does make a huge difference for some people, it all depends on the person.
Epsom Salt is a bit harsh so using something like magnesium orotate, malate, citrate or a gentler form than sulfate (epsom) can work very well. you want to take enough to give you diarrhea which means that you are fully saturated with magnesium.
people were doing flushes successfully in the 60's with no magnesium (further proof that there is no chemical reaction with the oil and the epsom salt). and some people do flushes without the magnesium, but for the first few it is probably best to use some form of magnesium.
some people and practitioners recommend enemas or colonics afterward. this is a personal choice.
for me, just eating a lot of fruit the next day works well, or you can just take large doses of magnesium again to flush out the large intestine. it is important in my opinion to get the stones as as quickly as possible because they are toxic.
hope this helps.
(pay no attention to these same two people who are trying to dissuade people from flushing, they are obviously waaaay off track!!! it's always the same two people too versus thousands of us who flush with great results)