Optical and IR data (black points) of Galactic sources classified as single C-rich post-AGB stars presented in Kamath et al. (2022), which we interpret as surrounded by carbonaceous dust in this study. The red lines indicate the best-fit model obtained using the DUSTY code (see Sect. 3). The grey line shows the SWS spectra from Sloan et al. (2003), when available. The derived stellar and dust parameters from this study for each source are shown in the different panels.