Consider using a source texture to paint on the mesh.
Your question now shows more of your progress.
Historical Note. At first I thought you were getting no texture paint results at all. Thus I encouraged you to use an image source and the simpler brush first as step 1 for major results. I estimated the clone brush could wait a learning period. From you edits above your are ready to use the clone brush.
TexDraw brush step 1. Clone brush step 2. Then you decide and refine in step 3 and beyond. Those are my suggestions.
Nooks and crannies that might not be visible in your reference photographs are suited to clone paint as your video shows. Some people also have top of head photos. Neck photos.
The interface of texture painting has changed since your video. I was not really emphasizing this change in the very capable and complex texture painting.
Apologies for lack of clarity.
Here is an image below.
The sphere is using a texture in this first image. This will be the target of your painting work. Under the Tools pane on left you see the human figure texture as the source of Stencil painting with a regular [TexDraw] brush. The Image editor windows show some results on the target texture. In the 3D View / Texture paint window. You see the large transparent brush stencil next to some finished painting work on the sphere placed in the distance. The arrangment is for discussion purposes.
A alternate image explanation.
Note the brush is a TexDraw brush. Brush mapping is Stencil. Do not use Clone Brush yet. First feel comfortable with the TexDraw. Clone Brush is a second step.
You may look at the history of this document to see the previous version.