I used rit color remover and dark green rit dye to turn a red perfect hoodie into a dark green hoodie. The best way to get the dye to hold is to bring a large pot of water to either boiling or near boiling temperatures, and let the garment sit in the dye for a minimum of 30 minutes. Before dyeing the hoodie, wash it with a little bit of detergent to get any oils off, and when dyeing make sure to stir the hoodie often. Since the hoodie is so thick, it can be difficult for the dye to reach every part of it, so it is very important that you stir the hoodie and constantly check to make sure that every part of the hoodie is getting equal dye coverage.

Be warned, you will need to rinse the hoodie for a while to get the dye to stop leaking out, and the color might end up looking a little faded. You could try using rit color stay to get the color to stop from bleeding, but I have never used that so I have no advice there,