I dont "flush" my systems until last week just before chopping them down, that week I run nothing but plain PH'd water and do an extra drain and fill halfway through the week. Other than that I drain and fill res every week and topoff during week as needed, alternating 1 plain gal then 1 nute gal for topoffs. as soon as plant has established itself, good roots and good growth, then you should be able to train. remember training and topping and such is done during veg so whatever you are going to do will add a lil time to grow table. when train, top or etc it causes mild stress. you then have to let plant recoup before doing more.