How do I increase ink flow?

Only a very small amount of ink comes out of the first stroke when I use the charcoal tools. I want more ink flow, how do I do that? When I check the setting, the flow is already at 100 but barely any comes out. I'm trying to use it at small sizes, (size 2 & 4) but at those sizes barely anything comes out and I have to go over a line multiple times. How do I change this?