To texture a 3D model with weight painting without Auto-rig, handle texturing (surface details) and manual weight painting as separate, independent steps—neither requires auto-rig tools.
Texturing adds colors, patterns, or details (via Blender’s Texture Paint, Substance Painter, etc.) and has no link to auto-rig (which automates rig setup). Weight painting—controlling how bones deform the model—is a manual task where you adjust bone influences directly, no auto-rig needed.
For beginners, use Blender: First, add textures in the Texture Paint workspace. Then, switch to Weight Paint mode to tweak bone weights—keep the two processes simple and separate.