The sentence tells you exactly what "'process' film" means—"devoted to the nuts and bolts of creation", that is, to a process. The quotes on "process" here indicate the author is either using some very-obscure term or (more likely, I think) is coining it themselves for their purpose in this piece, which is why (in either case) it's explained right after.

Pedantic, I think is used in the sense of schoolmasterly or in the manner of a teacher—as in: the film "reads" a bit like a lecture, is concerned with details and plainly connecting A to B in a logical order and clearly demonstrating that to the viewer, that kind of thing. That's why it's contrasted with "Yet it’s somehow also among his most immediate works" (emphasis mine). The author's saying it's not also excessively abstract or distant from life and applicability, as one imagines lectures might sometimes be.

Same root as "pedagogy", though outside certain educated circles "pedant" is almost exclusively used in the colloquial, pejorative sense of "know-it-all, especially one who insists on correcting others unnecessarily"—but it's certainly used in the older, more neutral sense here.