For beginners, mixing a normal map for a 3D model involves gathering source maps, blending in a texture editor, adjusting strength, and testing in a render engine.
Gather your base normal map (from model geometry) and detail maps (e.g., scratches, fabric weave). Use tools like Substance Painter or Photoshop—add details as layers with modes like “Overlay” or “Add,” starting with 20-30% opacity to keep details subtle.
Test the mixed map in Blender or Unity: if details are too sharp, lower opacity; if too soft, increase it slightly. Stick to simple layers first to avoid overpowering the base normal map.