In this paper we complete the description and application of a computational framework for the numerical simulation of first-contact miscible gas injection processes. The method is based on the front-tracking algorithm, in which numerical solutions to one-dimensional problems are constructed in the form of traveling discontinuities. The efficiency of the front-tracking method relies on the availability of the analytical Riemann solver described in Part 1 and a strategy for simplifying the wave structure for Riemann problems of small amplitude. Several representative examples are used to illustrate the excellent behavior of the front-tracking method. The front-tracking method is extended to simulate higher-dimensional processes through the use of streamlines. The paper presents a validation exercise for a quarter five-spot homogeneous problem, and an application of this computational framework for the simulation of miscible flooding in three-dimensional, highly heterogeneous formations. In this case, we demonstrate that a miscible water-alternating-gas injection scheme is more effective than waterflooding or gas injection alone.