Here is a summary of the steps presented in this guide:

\C0202021.\C484848 Import the object (press Tool>Import).

\C0202022.\C484848 Import the textures (press Texture>Import).

\C0202023.\C484848 Activate Edit Mode (draw in canvas, press Transform>Edit, hotkey '\C020202T\C484848').

\C0202024.\C484848 Assign Polygroups (Tool>Polygroups>UV Groups).

\C0202025.\C484848 Selectively show a region (Shift+CTRL+Click its group).

\C0202026.\C484848 Select the texture from the Texture palette.

\C0202027.\C484848 Shift+CTRL+Click in empty canvas, repeat steps 5 and 6.

\C0202028.\C484848 Export textures (press Texture>Export).
