To make these bold designs, use a stencil made from freezer paper -- it's waxed on one side and adheres to fabric when ironed. Then hold an outdoor paint-splattering session, peel away the stencil, and behold your stellar work.
On a protected surface, lay out a sheet of freezer paper large enough to completely cover the shirt's front. Draw or trace your star design onto the paper, then cut along the lines with a craft knife (a parent's job).

Lay the paper over the shirt (waxy side down), positioning the holes as desired. Using your iron's cotton setting, press the paper onto the shirt (a parent's job).

Slip a piece of cardboard inside the shirt. Lay it on a protected surface. Fill in the stencil with a background color. When the paint is dry, splatter and drip the other colors over it to create streaks and splashes. Leave it flat to dry overnight, then peel away the stencil.
To make the shirt colorfast, follow the directions on the paint package.