A session you can bend
Use one brush and fresh black paint. Compare a small batch thinned with plain water against a separate batch using diluted Flow Aid. Keep the brush and curve size the same.
Try 5 C curves and 5 S curves. Notice where the stroke feels effortless and where it starts to drag. Reload before forcing a dry brush onward.
Turn your favorite curves into three flame or feather shapes. One quiet, one exaggerated, one completely off the rails.