community of dyers

Im dying a baby wrap for a friend, and this blue twill DOES NOT want to take the dye! I'm so frustrated! I've dip dyed it and tried using a spray bottle to put the dye more directly on the fabric, and the ombré is so subtle once it comes out of the wash! I feel like I've wasted 2 days of my time! The wrap is a denim-ish blue color and I'm trying to get it to darken up with dharma procion in gunmetal grey. I tried adding imperial purple to deepen the color, but it only helped a tiny bit. I hate to admit it, but I'm a little afraid of true black dye, and don't own any yet. Any suggestions on what to do to get the stormy grad my friend wants?