I don't know how they did those stars and of course I'm new to AR... But maybe some stencils of stars, much like there are stencils for flowers and snowflakes in AR2.5.
If you drew one or two stars, then converted the layer to a stencil, you could use that to replicate the pattern.
Just an idea
solid black - punches right thru, so all the paint goes onto canvas
grey shades - partial transparency, so lets thru some paint
white - totally blocks paint and ends up red in the stencil
Hope I've got that the right way round!
Once you have some star stencils, use glitter and metallic paints to make them twinkle?
AR 2.5 Full Ed, Wacom Graphire Bluetooth A5 (Buggy!), MacBook Pro 15"