Not specific to the CPG realm, but I've had some very good luck working with the OpenAPI-devtools Chrome Extension[1] (previous discussion here on hackernews[2]) to discover the underlying APIs of various sites that I want to scrape data from.
This is a huge help, thank you. I've been using the Postman Interceptor extension, but OpenAPI-devtools looks tailor made for my use case. The hard part will still be figuring out the auth headers/calls (EDIT: the dev has added auth support since the HN post!)