  Cosmic-ray transport in astrophysical environments is often dominated by the
diffusion of particles in a magnetic field composed of both a turbulent and a
mean component. This process needs to be understood in order to properly model
cosmic-ray signatures. One of the most important aspects in the modeling of
cosmic-ray diffusion is that fully resonant scattering, the most effective such
process, is only possible if the wave spectrum covers the entire range of
propagation angles. By taking the wave spectrum boundaries into account, we
quantify cosmic-ray diffusion parallel and perpendicular to the guide field
direction at turbulence levels above 5% of the total magnetic field. We apply
our results of the parallel and perpendicular diffusion coefficient to the
Milky Way. We show that simple purely diffusive transport is in conflict with
observations of the inner Galaxy, but that just by taking a Galactic wind into
account, data can be matched in the central 5 kpc zone. Further comparison
shows that the outer Galaxy at $>5$ kpc, on the other hand, should be dominated
by perpendicular diffusion, likely changing to parallel diffusion at the
outermost radii of the Milky Way.
