Mix dyes then add some of each dye color to separate bowls.
Lay a damp shirt out flat on work surface.
Dip paintbrush into first color of dye and brush random strokes of color onto shirt.
Dip paintbrush into second dye color and brush randomly over the top of other brushstrokes. Cover with plastic wrap to keep damp. Let set 6 to 8 hours, rinse thoroughly and wash separately.