  In Paper I we presented a detailed formulation of the relativistic shocks and
synchrotron emission in the context of Gamma-Ray Burst (GRB) physics. To see
how well this model reproduces the observed characteristics of the GRBs and
their afterglows, here we present the results of some simulations based on this
model. They are meant to reproduce the prompt and afterglow emission in some
intervals of time during a burst. We show that this goal is achieved for both
short and long GRBs and their afterglows, at least for part of the parameter
space. Moreover, these results are the evidence of the physical relevance of
the two phenomenological models we have suggested in Paper I for the evolution
of the {\it active region}, the synchrotron emitting region in a shock. The
dynamical active region model seems to reproduce the observed characteristics
of prompt emissions and late afterglow better than the quasi-steady model which
is more suitable for the onset of afterglows. Therefore these simulations
confirm the arguments presented in Paper I about the behaviour of these models
based on their physical properties.
