Tape white craft paper down on a flat surface using clear tape on each corner.
Scatter rubber bands all over the paper. (This doesn't have to be perfect; it's okay if they overlap.)
Choose no more than four colors of acrylic paint and thin them with water, if necessary, to make them a runny consistency.
Dip the toothbrush into paint, then hold the comb a few inches above the paper and brush the toothbrush bristles over the bristles of the comb to create tiny specks of paint on the paper that look like airbrushing.
Repeat with different colors all over the paper, experimenting with holding the comb at varying heights above the paper and layering different colors.
Allow painted wrapping paper to dry fully before removing rubber bands and taking the tape off the corners.