Yeah so I've painted nebula's n' all on bookbags before but I never thought to SPONGE the paint! Awesome idea, it works amazing but you really have to BLEND BLEND BLEND before it dries too much and you have awkward splotches.
I painted these while they were on the ground, and for you girls with thick thighs, the paint WILL crack when you put the leggings on because its so heavily layered. My leggings were actually tight when I first put them on due to the fact the paint was layered when they were laying flat on the ground. I'll probably end up touching up the colors later on after they've been worn a bit, but I'll try doing that while wearing them to fill in any "cracks". ;D
Honestly, wash them a few times in cold water and they will be fine, acrylic stains fabric really well. I've painted a billion of my jackets before and the top-layers may crack a bit but after a few washes it will smooth out and there will still be vibrant colors all over the place.
Fun project! I'm gonna do all sorts of colors on clothes now, and I even bought silver and white fabric paint-pens for all the stars. :)