Watchband for a friend

Is it possible to go back and add some tooling to a piece that I have oiled and dyed? I was wanting to add my makers mark to a piece I have been working on. The stamp is being made currently and I did not wish to stop working on it. I went ahead and oiled and dyed it so I could continue working on it. I still need to antique this but this is the cover to my wallet.

I am going to stitch this watchband by hand. I have punched all of my holes. I will start at the watch and work down and around the band. I typically start with my work in my pony, with the stamped side to my right. I then start with the thread through the first hole, then take the left side needle through the second hole. I then pull it towards me and thread the right side needle through the same hole. Is this the correct way? I would start with the holes on the top of thi picture.

I am hoping to find someone to make me a makers mark stamp. Does anyone know of a company that makes good ones?

I am having a stamp made for my logo. One option is to get a heating handle. But I think it may work more like a brand. The tool maker said I would not need the heating handle that I can just use the striking mandrill on veg tan. Any thoughts/ experiences?