Hybrid hole-burning/fluorescence line-narrowing techniques are used to obtain vibrationally well-resolved emission spectra of squaraine chromophores in polymer matrices at 1.4 K. Standard fluorescence line-narrowing spectra of these strongly inhomogeneously broadened systems are complicated by overlapping emission from zero-phonon line (ZPL) and phonon-sideband excited molecules. The ZPL-excited contribution can be reduced either by preferential nonphotochemical hole-burning with narrow-band cw excitation or by partial saturation of the absorption with picosecond pulsed excitation. Subtracting the emission spectra of the ZPL-depleted samples from the initial spectra leaves predominantly ZPL-excited spectra exhibiting enhanced vibrational resolution. These techniques have been used to analyze the vibrational spectra of centrosymmetric squaraines, examine their phonon sideband structures in different polymers, and explore the temperature dependence of the width. We also probe the origin of the low-temperature electronic linewidth by combining cw hole burning linewidths, photon echo decays, and fluorescence lifetime measurements.