I start all my seeds in soil and transplant to water. I do it while their still in solo cups so it's easy. Just get a 5 gallon bucket of water and dunk your root ball in and out of the water. I always have small sticks n shit still stuck to the roots but it won't hurt anything.
I did recommend him washing the soil off the roots. I will concur...
Even tho, this is not the way i would recommend to a newbie, and I deff wouldnt do that.
How ever i moved for mothers in coco, to rdwc to flower them out. It was rough and it took all my growing experience to get to the end, which I did :) But I had ph, ec, root rot, issues
Had to use ogbiowar tea to get them healthy again all during flower!
He asked if he could plant the root ball in the grow pot, and just let the roots grow in to the water...
What he isnt accounting for is he will have to top water till the roots go down in the water, and each time he will wash soil (mud) into the system to clog the filter sooner or later and prob flood the system, or burn up the pump...
I would just take clones and do what I said, and flower the mothers out in soil, after taking a clone to restart your mother...