Despite their ubiquity in day-to-day life, bulk granular materials have surprisingly complicated mechanical properties. As a result, problems such as predicting the flow profile in a draining hourglass have proven to be a significant challenge. This talk constructs and tests a general continuum model for dense granular matter, which can be used to predict the stress and velocity profiles in well-developed flows. Recent models for granular elasticity (Jiang and Liu 2003) and rate-sensitive plastic flow (Jop et al. 2006) are reformulated and combined into one universal elasto-plastic law, capable of determining flowing regions and stagnant zones simultaneously in any arbitrary 3D flow geometry. To merge the responses, we enforce a Kroner-Lee decomposition and constrain the constitutive laws to obey necessary physical principles. The model is numerically implemented as a VUMAT in ABAQUS/Explicit, and results are directly compared to experiments and discrete particle simulations in several inhomogeneous flow geometries. We conclude with an evaluation of the overall breadth of the model, and provide preliminary arguments for how to enhance the description using non-local quantities.