I usually mix them in the tank after I clean it and then spray it to add a little bit of humidity to the coco husk, then mix it together again. I don’t think it would hurt to mix it together in a bag or storage bin for later use though as I’ve never had either ingredient mold on its own or when together.
Also, the 2:1 ratio was just a rough suggestion so don’t feel like you have to follow that exactly. I just make sure there’s more cocohusk than cypress mulch because I feel like the coco husk holds humidity better than cypress mulch, plus I think it just looks a little better that eat.