THIS REQUIRES HAVING AN OBJ of the brush you are adding, OR a .vdm (vector displacement map) texture.
It covers making a .vdm from an .OBJ and using a .vdm to use as a brush in Blender's sculpt mode.
Is there probably a better way to do this than using a shrinkwrap modifier?
Yes.
Am I too lazy to figure out another way to do it instead?
Also yes.
Now go forth and buy brushes for zbrush to support small artists, with the knowledge that (if an .obj/model or .vmd file is provided by the artist) you can convert it to work with blender! Yaaaay!