It depends on your location , it has been said that because they are outside that they don't need thinning out and in the perfect environment that's true but here in the North east our humidity levels go through the roof so after the third week of bloom I defole very aggressively I take all the fans I can ,all the small stuff on the bottom ,anything that doesn't have Pistil's showing .
I finished these 2 yesterday you can see the light difference from before to after by looking on the right side of the pic those are plants I haven't done yet hope this helps