I'm trying to create custom brushes in illustrator with scanned brushstrokes. I use image trace, then expand...how do you then select and delete the white background?
As mentioned above by @joojaa, you have to tick the "Ignore white" in the advanced settings in trace window. If this option is disabled/grayed out then make sure you pick the first method type (Abutting). Since you have already traced the brush, you can use the magic wand tool to select all white shapes and then you can remove them