No need to flush super soil.
I just switched over from liquid nutrients. I made my own variation of subcool's recipe based on what I had available and my budget. 2 weeks into flower, my plants are happier than ever.
I'd link you to the subcool recipe if I knew how. There's a whole page on here about it.
One thing to keep in mind is that your soil will need to "cook" for a few weeks before it's ready to plant in. You could easily start your plants in another soil without all the amendments added to it and cook your super soil until the plants are ready to be transplanted.