In this contribution we review recent progress with fixed-or der QCD predictions for the production of a vector boson in association with jets at hadron coll iders, using the programs B LACKHAT and SHERPA. We review general features of next-to-leading-order (NLO) predictions for the production of a massive vector boson in association with four jets. We also discuss how precise descriptions of vector-boson production can be applied to t he determination of backgrounds to new physics signals. Here we focus on data-driven backgrounds to a missing-energy-plus-jets search performed by CMS. Finally, we review recent progress in developing theoretical tools for high-multiplicity loop-computation within the B LACKHAT-library. In particular, we discuss methods for handling the color degrees of freedom in multi-jet predictions at NLO.