You have 2 options-- uproot the plant and shake off the soil & rince the roots-- then put in the DWC bucket-- Water & carbs only.... change the water 3x the 1st day, 2x the next day and 1x the 3rd day... otherwise, the remaining soil attached to the roots mucks up the works....
IF you choose to chop it 1st--- be CERTAIN that she is already well hydrated and NOT about to wilt-- or she will!!!
DO NOT to separate branches because the main is USED to transporting the water & nutes to the rest of the plant..
change the water every day and flush at least 3 days.. especially with MG.. or it may be pretty be harsh or even smell like hay when dry....
Done it a lot in the past in our 'early years' of growing- and it works well !