You can get over 2,400 branches in under 5 minutes at the location in my bark gathering video. Just use a Pickaxe or hatchet. (Pickaxe will get bark too).
Also don’t forget to use an artisan thrall to cut the costs. You can use pretty much anything on the artisan’s table. Just slap a T3 or 4 in there and it’ll cost only 50 branches per palisade; 10 branches per spike, 5 spikes per wall.