sculpy is the way to go,
youll need to sculpt the small parts you wanna add on,then bake them seperatly in the oven.let them cool over night and the parts will be pretty hard.you can then use 2 part epoxy to glue them onto the helmet,youll need a real good adhesive like epoxy to hold them on without fear of them coming off.
you can also rub a small coat of epoxy right onto the sculpy parts themselves to seal them.be sure to follow the instructions on the cooking time,over cooked parts can warp and burn.sculpy is great to work with cause if you make the part and dont like it,you can squish it into a ball and start over!LOL
if you are making large parts that need to be molded right onto the helmet itself,then check into the non-bake sculpy.cant recall the name of it but i know it exists.if your making small details like the horns on the rim of the wolf bio then regular sculpy is great.
hope that helps