I’m looking for a course that’ll truly upgrade my materials skills for hard surface modeling.  I don’t have substance painter, but I’m in the process of learning GIMP for creating bespoke textures.  Any suggestions?
Pothead is always the go to course for that:
https://cgcookie.com/courses/pothead-create-a-hard-surface-character-in-blender
But really anything that deals with shading something, you can always watch and walk away from it with tons of shading and materials knowledge:
https://cgcookie.com/courses/luminor-create-a-vintage-camera-with-blender
https://cgcookie.com/courses/basemesh-create-stylized-characters-quickly-with-blender
https://cgcookie.com/courses/sessions-macro
https://cgcookie.com/courses/sessions-minimalism
And if you want to go OG, there's always Sci-Fi Helmet:
Thanks so much!  I’ll def check those suggested courses out. :)