Well I got the box of goodies today to refurb my 'just starting to wear' bolster on my drivers seat.
Just kept on adding black to the mid grey base colourant until it matched the seat. Spread a few drops of the resulting mix onto the worn area, spread it with a piece of foam (supplied) and dried it with a hairdryer. I then applied a mix of gloss and matt sealer to the coloured are and dried that off as well.
The end result is perfect, you just cant see any change in colour from standard. It took 30 minutes to do.
So a big thumbs up to the leather repair company.
I would imagine an application of mainly matt sealer would get rid of shiny steering wheel syndrome as well.