  In a set of two papers, we propose to study an old-standing problem, namely
the electromagnetic interaction for particles of arbitrary spin. Based on the
assumption that light-cone helicity at tree level and $Q^2=0$ should be
conserved non-trivially by the electromagnetic interaction, we are able to
derive \emph{all} the natural electromagnetic moments for a pointlike particle
of \emph{any} spin. In this second paper, we give explicit expressions for the
light-cone helicity amplitudes in terms of covariant vertex functions, leading
to the natural electromagnetic moments at $Q^2=0$. As an application of our
results, we generalize the discussion of quark transverse charge densities to
particles with arbitrary spin.
