The best way to discover brush strokes is to play with each shape brush you have and see what happens! I have painted for over 30 years and still find new ones. On a more serious note, a discipline which really helped was when I studied one-stroke folk art- English canal boat or Russian- they use similar techniques; it really does make you focus on making the right mark with an appropriate brush, and is actually harder to master in acrylic because the rapid drying time affects the paint's flow properties. It will also teach you how to load brushes with more than one colour so the mixing happens on the support which gives much more vibrancy to your mixes. Hope this helps, truly, experimentation is the way forward!