Black holes are the most extreme and compact objects in the universe. Since their theoretical prediction, scientists have tried to shed light on these objects that swallow everything that comes close to them, including light. This is a fascinating paradox that poses difficult challenges to study black holes in the universe. Fortunately, these objects leave their traces imposing their extreme gravitational pull on the surrounding matter, while it is falling into the black hole. The REWARD project aims to study accreting black holes in order to obtain the most accurate measurements of their two parameters: spin and mass. Such measurements would allow, for the first time, to reconcile the tension from gravitational waves and X-ray models, and build a coherent picture of black hole phenomenology. Recently launched X-ray missions (e.g. NICER, NuSTAR) have provided unprecedented high signal-to-noise energy spectra and fast timing resolution observations, which require a new generation of models for their interpretation. In order to do it, I will combine hydrodynamics simulations with X-ray models. In particular, I will model radiation reflected from the accretion disk, accounting for the simulated 3D density structure of the disk. I will compare these new models with X-ray observations of accreting black holes, and I will provide robust spin and mass measurements of those systems.