Waves remitted from a scattering medium carry information that can be used for non-invasive imaging and sensing. Such techniques are usually limited by a low photon budget. Recent progress in optical wavefront shaping has enabled coherent control with an order-of-magnitude enhancement of remission [1]. This experimental study necessitated increasingly demanding numerical simulations. Extending this line of research requires more sophisticated computational techniques capable of simulating multiple instances of even larger systems. Here, we demonstrate that remission geometry can be efficiently simulated using a novel open-source software package [2] Maxwell's Equations Solver with Thousands of Inputs (MESTI). To verify its numerical performance, several simulations and comparisons with the method used previously are presented. Excellent qualitative and quantitative agreement with previous results is obtained. Additionally, orders of magnitude improvement in the computational performance of MESTI is observed. This opens the path to computational modeling of spectral and temporal remission from large scattering systems.