Beginners painting a roughness 3D model should use a user-friendly tool (like Substance Painter or Blender’s Texture Paint) and focus on mapping surface smoothness—low roughness for shiny areas (metal, polished plastic) and high for matte/worn spots (fabric, dirt).
Roughness maps tell the renderer how light behaves: low values mean sharp reflections (smooth), high values mean scattered light (rough). Start with large sections (e.g., a cup’s ceramic body as low roughness) then add small, natural wear details (scratches, fingerprints) to make the model look real.
If you’re new, practice on simple shapes (like a sphere) to test how roughness changes the look—this builds confidence before moving to complex models.