there is an local indy MB/BMW lot i visit frequently that "dyes" almost all the interiors they receive/sell. they do both tex and leather on alot of really high-end cars.

i am unsure of the exact product, but they use a airbrush for the application.

the finished result is great! interiors that i thought looked good before, looked brand new after the dye touchup, especially the drivers seat that receives the most daily wear. it also works well on any areas that were sun faded.