Affordable large-scale energy storage systems with improved capacity are crucial to a sustainable energy future, and the great availability of Na in sea water makes Na-ion batteries a very attractive choice for stationary energy storage. A promising class of cathode materials for applications in Na-ion batteries are the layered sodium transition metal oxides, NaMO2 (M = Fe, Co etc.). We set out to generalise our QENS analysis (which already accounts for coherency effects) to mixed coherent and incoherent scatterers, such as Na. NaFeO2 is chosen as a starting point due to its electrochemical activity, simple structure as well as low incoherent scattering contributions from the static lattice. Understanding the diffusion mechanisms in this simple layered material is vital for subsequent successful investigations on more complex systems (containing multiple transition metals).