Acrylic paint is your friend. It's water-based, so it won't kill you or make your apartment smell funny or catch fire. It dries fast and looks neat. There are sparkly colors and fluorescent colors. Take extra white and black if you're going to be doing more than four stashes.
Acrylic paint rubs right off skin once it's dry, but it stains cloth forever.
Don't wear fancy pants while you work. You have to varnish acrylic paint, or normal handling will damage it. I used clear gloss acrylic-based stuff. It's full of turpentine, so it does smell funny and rot your liver. Use with ventilation.