how can i make my eyebrows fuller / darker?

i have to say that i like the natural / fluffy but still slightly shaped vibe of my brows, but i think they could be fuller. i tried castor oil a few years ago and that helped with growing them back, but it didn‘t make them fuller. eyebrow dye makes me break out sadly :( also what do you think about cowlick brows? i personally love the look, but never realized i have them