  The transmissions as functions of energy are central for electron or phonon
transport in the Landauer transport picture. We suggest a simple and
computationally "cheap" post-processing scheme to interpolate transmission
functions over $k$-points to get smooth well-converged average transmission
functions. This is relevant for data obtained using typical "expensive" first
principles calculations where the leads/electrodes are described by periodic
boundary conditions. We show examples of transport in graphene structures where
a speed-up of an order of magnitude is easily obtained.
