Thanks James...No I do not use vinegaroon or similar things ( I have never seen that thing!) ...here we use alcohol based dye, made in Italy, obviously (Nero d'Inferno is the name of the product)
About the how to do that work with wet-leather....it depends from many factors ...one of them is our leather tanning, other is the position of design....and - not the last reason- the way to use the hands molding the leather around the foam....look more on FACEBOOK : Sergio Falco)