first off mate make sure they are well rooted thro 3 or 4 inch rockwool cubes before they go in the system , when they do go in id start the pump 15mins per hour for the first week to tease roots onto the tray
then when theres roots put the pump on full time only trickling tho
id put a vhs case or similar under the pump end to slant the tray and create a better run off
dont cram to many in the system if its the nft424( 1.2 meters long ) then id do 6 plants max mate
id start them of by hand watering until the pumps go on , id think about keeping a mother cos the problem with seeds and nft is males . once the roots become tangled its a nightmare to remove them .
theres 2 things to do , either cut the plant completly and treat with cannazyme and hope the dead roots from the males dont rot
or leave the males with just enough leaves to stay alive and pinch out male flowers
i would veg for as long as poss in the 3 inch cubes , i have kept clones in these cubes in plastic trays for upto 4 week (with clones) this way by the time they show sex there shouldnt be to much roots down and in this case id go with killing the male and cannazyme . if theres loads of roots down i personly wouldnt kill the plant , others would
i know alot to take in , just keep coming back to this as you need it . worked for me when i ran nft
good tank management is vital , so get a good ec and ph meter
but sort some mothers or even 1 mate clones make nft much easier