Here is a display of using a blend node and a mask to apply makeup to the face. Its easy enough to do but you need to figure out where in a material to insert the node if its a complex shader.

In this case theres some nodes attached to alternate diffuse so I have left those alone. The face image map feeds into the top of the blender node. The second value is the color , or it can have an image map attached for things like tattoos. The mask image feeds into the blend value.

As you can see the mask has a soft edge so it  fades into the surrounding skin. You have to create your own masks in a paint ptogram and its done on the uv map template for the face. [ I dont paint stuff so I cant say more than that] 

For the lips you would maybe mask the lip material and not go outside it, or color the lips and mask the face_skin material to blend it in. The same mask will work in both materials.

I have painted in the new connections in yellow to make them clearer, the red line is the original connection of the face image to the diffuse channel.

left click on the diffuse  channel end and select disconnect if you dont use the material room much.  click and drag to connect the new nodes .

• the mask has a v offset because it is for V3 and I am using it on V4 so the lineup needed adjusting.  The mask is from A_  Ria character that was in the store here.
   
  This is a way to add tattoos, scars , makeup, bloodstained mouth for vampires etc , without doing it in postwork. The blend nodes can be stacked to add more layers if you get the order of them correct. It needs to be rendered to see it.