I don't know if its the same with you guys but, when i make a new brush i can't get away from using it exclusively on a new canvas.
i made a new brush this morning, and used it for my morning warmup. the painting ended up pretty muddy and meh, but the it was all about the brush.
i left the sample on the left for anyone interested in seeing it (i'm sure everyone has an equivalent if not the same one kicking around), the spacing flow and texture was a lotta fun playing with. but the fine details were a pain in the ass, it didn't like being painted with when it was any smaller than 10.