Hey, what you want to know. Doing defol in wk 3 of flower is not optimal. But if you feel the need to do it if you are lacking light pen. Then start at the very top. Leave as much growth as you can on the bottom espically if its not covering anything as what is the point in taking something that brings in energy that's not blocking out any light. So yeah focus on the top as the goal is to allow light to reach the lower bud sites/leafs. So, if say your top bud sites has 4 main fan leafs/sugar leafs you want to remove no more than 1/3 in this late stage of flowering if you'd done it earlier you could of taken more but as their won't be much if any new fan leafs be very careful taking them, leaf tuck where you can. But 1/3 and remove leafs you think will grow over a potential site and remove some you see that are fully blocked out of the light either by buds or whatever as its just a food taker now giving no energy in return. Keep healthy leafs and even if u see leafs that are some what healthy or only have light defs leave them, that also goes for any NPK defs that might suck food out of lower growth leave them till they fully being food for your plant right up until they aren't anymore (meaning their dead). Feel free to DM me if you want more details. But only do it if u feel you have to. As you are moving into mid-flower soon if u are in 3 was of flower you need as much energy as each leaf can bring in. Good luck pal..