you can use cold porcelain or sugar paste for modelling.
I'm using cold porcelain and a 5cm ball, modelling tools and 3d eyes.
cold porcelain: nicron
3d eyes: 3d ojos autoadhesivos de Mariela Lopez
tools: Cerart
I suggest you to look at Bia Pastry & Tips channel, it's a new channel to make amazing cakes: https://www.youtube.com/channel/UCgnB3HLl2MKG-ms9dtwOsuA