  We apply a recently developed variant of the Density of States (DoS) method,
the so-called Functional Fit Approach (FFA) to two different models: the SU(3)
spin model and SU(3) lattice gauge theory with static color sources. Both
models can be derived from QCD and inherit the complex action problem at finite
density. We discuss the implementation of DoS FFA in the two models and compute
observables related to the particle density. For the SU(3) spin model we show
that the results are in good agreement with the results from a Monte Carlo
simulation in the dual formulation, which is free of the complex action
problem. For the case of SU(3) lattice gauge theory with static color sources
we present first results for the particle number as a function of the coupling
for different values of the chemical potential.
