Intimate contact between the surfaces takes place by normal and tangential forces (friction). Lattice-Boltzmann and DEM methods have been used to analyze frictional flow, particle collisions and solving Navier-Stokes' equations.Any collision between toner and developer can result in charge exchange that depends on dielectric relaxation. Charge transport processes in disordered complex media are accompanied by anomalously slow relaxation for which usually a broad distribution of relaxation times is adopted. To account for those properties of the environment, a standard kinetic approach in description of the system is addressed either in the framework of continuous-time random walks or fractional diffusion. A model can be constructed which assumes collisions between toner particle being elastic-plastic and an elastic carrier particle. Charge transfer takes place during each collision and the collision frequency is derived from particulate flow of cohesive particles. Charge to mass is analyzed for dependence on toner particle size, charge mobility, dielectric relaxation and yield stress (modulus) of toner and carrier surfaces. Model predictions are compared with experimental results.