It is definitely possible to add clothing and hair to Makehuman models. You can use software like Blender to import the Makehuman model and then add clothing and hair using Blender's modeling and sculpting tools. There are many tutorials available online that can guide you through the process. As for tips and tricks, it's important to pay attention to the topology of the model when adding clothing and hair to ensure they deform correctly with the model's movements. Also, make use of reference images to achieve the desired look.
Regarding the link you provided, it seems to be unrelated to the topic of creating avatars with unique facial appearances. Connections Game