In this Blender 2.8 texture painting video tutorial I show how to texture a simple object / mesh using different stencil images.
The model is UV unwrapped with smart Uv unwrapping (lazy techniques but for texture painting it works), then I added a base color slot and paint using the default draw brush, the stencils have an alpha background, and alpha is used as a mask in the principled shader.
Fire warning texture can be downloaded here:
See my social profiles here:
Production Music courtesy of Epidemic Sound: http://www.epidemicsound.com