Add custom smoothing dynamics to your brush. This will give you similar smoothing results as the normal freehand brush. There are a couple options that you can change.
Average your movement to make it appear smoother. Higher values will make your brush move slower.
- Faire glisser
A rubberband effect that will help your lines come back to your cursor. Lower values will make the effect more extreme.
Recommended values are around 0.02 Mass and 0.92 Drag.