Photon buildup factors provide a convenient method for radiation protection professionals to calculate dose and exposure behind various shielding configurations. Examination of buildup factors can also provide insight into the behavior of photons in these shields. Recent work has developed dual-layer buildup factors for several shielding configurations and a limited number of energies while slant-path buildup factors have been developed for single-layer shields. This work develops slant-path buildup factors for slab-geometric, dual-layer shields comprising polyethylene and lead at 25 energies conforming to the energies used in the buildup factor standard ANSI/ANS-6.4.3-1991 (W2001), “Gamma-Ray Attenuation Coefficients and Buildup Factors for Engineering Materials,” between 10 keV and 10 MeV. Further, the increased energy resolution of the calculations performed in this work allows the energy at which the previously identified “buildup reversal” phenomenon occurs to be more precisely identified. The effect of mesh spacing and quadrature resolution on fluence through the shields is also considered.