>>2908362If I remember right with that what you do is like you said.
>extend white canvas for draw in part>inpaint sketch or draw in photoshop / gimp a rough outline of the partsIt helps here if you do color match so the AI picks up on it
>Put it into inpaint and run that portion only through inpaint Adjust noise til you get something you want
>Keep repeating adn when you think it looks good and want to match send it to img2img and run the whole image over a few times at low denoise to smooth out the inpaintBallpark is the idea the actual levels are just gonna depend on what you consider good for it.