If you are using a variable temperature tool, please do several test burns to determine the maximum heat setting that you will want to use. Variable burners reach a far hotter temperature so you need to avoid the highest setting so not to scorch the leather surface.
For my variable tools I use either a loop pen tip or small ball tip to create the fine lines needed for this project.
To create the stark white and black impression of the Mayan Hieroglyph use light pressure and a scrubbie stroke to fill in the background areas of each square.
Using your wood burning tool in an upright hand position, work your tool tip over the design elements to create a thin, even black line.