Spotone is the best way to go and it's critical to match image colour (warmth) or it's going to be noticeable, You also need to build the colour up slowly, the principle isn't to try and make an exact match rather to reach a point where the spot becomes un-noiceable.
I've one negative where I was shooting udergrapund in an abandonded MAnganese mine and my arm and flash gun show up, I had three others helping me paint the cavern with light
I was around the entrance to the adit to the right, it took me asome time to retouch it wasn't difficult just painstaking. I did it in two step rather than rush it.
Somewhere I have a Johnson's retouching kit with dried out dyes easy to rejuvenate and a set of three different colour blocks of dye for B&W retouching. These thingas appear at Camera Fairs but mine came over 20 years ago in a job lot of darkroom equipment.
The advantage of using these specialist dyes is it's easy to colour match and the results are invisible when done right.
Ian