Computer modelling of atomic processes on surfaces and bulk materials has seen great progress in the last decade due to the advent of semiempirical methods. In this work, we extend the scope of these techniques to deal with thin films, an area where the progress in large scale atomistic modelling lags behind similar process in bulk alloy design and surface structure analysis. These techniques rely on solid theoretical background and provide the computational economy that allows for the treatment of complex problems. We discuss one of these techniques, the BFS (Bozzolo-Ferrante-Smith) method for alloys, and illustrate its application to the problem of thin film formation. In particular, we show modelling results on the formation of binary and ternary films of Ni and Al with either Ti or Cr alloying additions. Differences and similarities with the corresponding ternary bulk alloys are discussed. Radical changes in layer-by-layer composition are observed in both cases. While Ti additions induce the formation of a particular ternary phase close to the (110) surface, Cr additions result in the formation of an alpha-Cr precipitate close to the surface in addition to the changes in surface composition.