I'm not personally familiar with the mods in question, but yes, you will need to edit the Enchantment itself, or more properly the mod in which the enchantment is found. To do that, you will most likely have to merge the two mods, unless the facemasks use an "ArmorType" keyword from a .esm on which the mod that contains the enchantment is already dependent (one found in vanilla, or DB, etc). In the ENCH entry for the enchantment you want to change, there is a field with a dropdown list called "Worn Restrictions". The item that shows in that space is a formlist made up of keywords. Just add the "ArmorType" or "ClothingType" keyword for the masks to that formlist and save, everything should work just fine. If for some reason the facemasks don't use an armortype or clothingtype keyword (or some other unique keyword for the masks) you will also need to add the same keyword to each of the masks as well. AFAIK it's not enough that the keywords have the same name, they need the same hex code as well, meaning you can't just add a new keyword with the same name to one mod and have the mods work together correctly. Each item has to reference the same keyword (in the same .esp or .esm).
