You can create shaders for 3D models without Photoshop using shader editors in 3D software (e.g., Blender’s Shader Editor, Unity’s Shader Graph, Unreal Engine’s Material Editor) or standalone tools.
These tools use visual/node-based workflows to adjust material properties (color, metallic, roughness) and build effects (reflections, transparency) directly—no image editing needed. You connect nodes to define how light interacts with the model’s surface.
For beginners, try Blender’s free Shader Editor: it has simple tutorials for basic shaders (like wood or glass) that don’t require external software.