Bark is a product of smoke, rub, and air flow.
A course rub will make better bark than a powdery rub. Theory is, it creates more surface area for smoke to adhere. And a powdery rub will block smoke from the meat surface. Just simple S/P will make a dark bark.
Moisture on the meat attracts smoke. Meatheads' PHD over at Amazing Ribs has done a good experiment showing how wet objects attract smoke. I keep a water pan in my smokers and spritz.
Good air flow will come with the type of smoker. I think about any stickburner should have good enough air flow to create good bark, though I know that my Franklin makes better bark than my Brazos did. But both creat dark bark.
My Masterbuilt 560 GF had good air flow and created dark bark. It had better air flow than my Assassin 17 GF. But my WSM never did, just not enough air flow. I suspect the kamado type cookers are the same.
There's a theory going round the internets that slowing down air flow will give the smoke particles more time to attach to the meats. Something about the smoke " lingering " in the cook chamber. My experience says that's a false idea. I got better bark with stronger air flow.
And that's about all I know about that.
This was the only brisket I smoked on the 560 GF, it made a nice bark. It was a cute little 9 pounder.