Looking at the face...it has kind of a rough texture.
You're using oils, right? It was this texture that drove me, thankfully, to Andrea/Vallejo acrylics.
Try thinning the paints a bit more. Maybe add some Liquin. I forget who makes it but it's in the same area s oils.
Do you use "artist" quality oils or "student?" The artist variety has finer pigments and should also help reduce the graininess.