Reactive Molecular Dynamics simulations were run on three epoxy-amine thermoset systems, with different hardener monomer functionalities. From the obtained reference data, the degree dependence of the monomer reactivity was obtained as a function of the conversion of functional groups. Monomer reactivities were calculated and used to parametrise a polymer model including the First Shell Substitution Effect (FSSE). The model is used to run numerical simulations on a graph. Results are compared to results from graph simulations using the independent functional groups model (ideal polymerisation), and from the benchmark Molecular Dynamics simulations. With the parametrised FSSE model, it is possible to give more accurate predictions of the relevant properties of the polymer, such as the gel point.