If you feel unsure of any aspect of a purge, then it is right for you to avoid it. One of the best flushes I ever had was Dr. Sutter's. No magnesium of any kind added to his method. However, my second-best did include Mg Sulfate, which I just hate, but it worked wonderfully.
As Dr Sutter says, "mix and match" (ie, invent your own flush based on common sense and previous experiences). Figure things out for yourself after much reading and maybe some consultation with others, such as Telman, for example.
However, Mg or no Mg, I keep that little bottle of Mg Sulfate on hand for any scary symptoms such as pain during an attempted flush. If a person is low on minerals (ie, in a weakened condition), they should not try any flush if you ask me, because yes, then you are risking excessive loss of electrolytes.