Flushing nutrients out of soil BEFORE the grow?

If using MGOC at 50/50 perlite:soil ratio, could I set up my pot (with nothing in it) and flush it 2 or 3 times before I plant anything in it to flush the already existing nutrients out?

Yes, you could try it, but it isn't necessary, especially if you've added 50% perlite. IMO, when growers think their MG soil is burning their plants, they're actually drowning them, because they have overwatered, and it's taking too long to dry out. I've used the stuff for my first couple grows, throughout every stage of life, and never had a problem with overfert. And, with that much perlite added, you won't have any issue, either.

thanks man! repped with my puny rep power