What am I doing wrong? I've bought 2 different brands of pens, draw my Mickey head silhouette on t-shirt and let sit for 15-20 minutes. When I rinse the shirts off, nothing, nada, no bleach outline like the cute ones I've seen on the disboards. I thought it was 15 minutes; am I supposed to let it sit longer? The spray bleach shirt worked great but this has me stuck! Thanks