I present Picard, our newly developed code for the numerical solution of the cosmic ray transport equation with a focus on Galactic cosmic rays. This code applies contemporary numerical solvers that allow an efficient solution of 3D models on very high resolution scales. Picard also includes features that have been introduced by other groups in the context of Galactic cosmic ray transport, like anisotropic diffusion and non-axisymmetric cosmic ray source distributions. I will contrast the properties of the new numerical solver with other approaches for Galactic cosmic ray transport. The capabilities of Picard will be illustrated by a discussion of results for spiral arm cosmic ray source distribution, where I discuss the consequences for various observables related to cosmic rays, like the cosmic ray spectra and the resulting Galactic gamma-ray emission.