  We report here methods and techniques for creating and improving a model that
reproduces the scintillation and ionization response of a dual-phase liquid and
gaseous xenon time-projection chamber. Starting with the recent release of the
Noble Element Simulation Technique (NEST v2.0), electronic recoil data from the
$\beta$ decays of ${}^3$H and ${}^{14}$C in the Large Underground Xenon (LUX)
detector were used to tune the model, in addition to external data sets that
allow for extrapolation beyond the LUX data-taking conditions. This paper also
presents techniques used for modeling complicated temporal and spatial detector
pathologies that can adversely affect data using a simplified model framework.
The methods outlined in this report show an example of the robust applications
possible with NEST v2.0, while also providing the final electronic recoil model
and detector parameters that will used in the new analysis package, the LUX
Legacy Analysis Monte Carlo Application (LLAMA), for accurate reproduction of
the LUX data. As accurate background reproduction is crucial for the success of
rare-event searches, such as dark matter direct detection experiments, the
techniques outlined here can be used in other single-phase and dual-phase xenon
detectors to assist with accurate ER background reproduction.
