Augmented Reality (AR) applications have been announced as promising for remote assistance in Industry. However, there is a gap of human-centred design processes informing the design of technology for such contexts. In this paper, we report the phases of a human-centred process to inform the design of an industrial AR application for remote assistance for maintenance workers, which included worker interviews, and a sequence of usability tests conducted with dyads, using handheld and head mounted displays. With this paper we contribute to the still emerging body of knowledge on the practical applications and implications of human-centred research processes in industrial settings and discuss how the familiarity of dyads may impact the usability of AR applications for remote assistance in Industry 4.0.