I'd like to score pages of 13x19 Entrada Bright Rag for a custom binder. How do I do this myself to achieve similar results as your pre-scored Chinle pages? Should I perforated the paper and with a needle? Should I slice the paper with a razer? What tool is best to use and where to find or make one? Thanks.

There are many different options for scoring Entrada- what tool you use depends on how much you want to spend, and how automated you want the process to be. I would recommend searching for 'paper scoring tool' online to see your options and different techniques. I recommend against perforating or slicing with a blade, both of those will weaken the joint and increase the possibility of the paper tearing along the fold.