  A crossing symmetric $\pi N$ scattering amplitude is constructed through a
complete attachment of two external pions to the dressed nucleon propagator of
an underlying $\pi N$ potential model. Our formulation automatically provides
expressions also for the crossing symmetric and gauge invariant pion
photoproduction and Compton scattering amplitudes. We show that our amplitudes
are unitary if they coincide on-shell with the amplitudes obtained by attaching
one pion to the dressed $\pi NN$ vertex of the same potential model.
