My Lustrum Darkroom book is at work, but from what I remember, he didn't just process in Rodinal for the sake of it, but applied agitation depending on how he felt about the shots. ie for more contrast, grain and accutance, a bit more vigorous shaking was applied. However, as Steven above suggests, following another photographer's formula will not give the same results. Ralph Gibson's work has that intensity because he learnt what his camera, film, papers and developers could do. For me that's a very inspirational credo. Now where is that roll of Tri X?