Read his book "Hunting the Hard Way."
Chapter 9, page 115.
There is no "one way" he made shafts/broadheads. The film clip of him making arrows was 1930s in California and varied even from the method used in the late 1920s in Opa-locka, Florida. Hill's arrow making evolved along with everyone else's into what it has become today.
Arrow making was a tedious process and Hill, like many others, began purchasing shafts/arrows from commercial operations as these sources developed. According to Ben Pearson Jr., Hill and Ben Pearson enjoyed a long and close relationship. We know most of the arrows if not all that he took to Africa were provided by Pearson. It is likely he purchased or was provided them for services for a number of years later in his career. But, I suspect, he could still "roll one by hand" in a pinch.