Analytical and numerical solutions that describe the coupling between bright and dark spatial solitons, located in separate planar waveguides are presented. The analytical theory rests upon a well-known variational approach and it is shown to be in good qualitative/semi-quantitative agreement with the exact numerical solutions of the coupled equations of the problem. By manipulating the soliton ‘masses’, through the input power, interesting trajectories for the solitons can be selected. Indeed, these trajectories are shown to possess behaviour patterns that qualify as the first steps in a design of an all-optical scanner. At all stages, the variational solutions are thoroughly checked by the numerical simulations and found to have excellent predictive qualities.