I got a coal with red cedar spindle and hearth bowdrill a couple days ago. I struggle with the harder woods like red cedar. They require greater speed and less downward pressure which requires more control and better form. I am a bit klutzy and have trouble maintaining speed without the spindle spitting out and sending my precious dust everywhere.
The dust from harder woods is usually fibrous, causing the dust to not form a dense enough pile. Its like putting a match to the average game of pick-up-sticks, they’re just to far apart to allow the heat to transfer from one to another.
So less pressure makes finer dust, and more speed makes up the heat lost to lower pressure.
I have not done scientific research on this, someone else could probably give a better explanation to what is going on, physics wise, but I think this explanation as useful as any.
So I will keep practicing. You never know when a harder wood is all you got.