A technique to facilitate the assignment of congested high resolution IR spectra is presented. It involves subtraction of component spectra simulated from known spectroscopic constants. Application to the v2 (1313.1 cm-1) and v7 (1351.7 cm-1) bands of CHC1F2 led to rovibrational line assignments for less intense and overlapping features including the minor isotopomer CH37C1F2 and c-type lines of CH35C1F2. The number of transitions assigned to the fundamental bands increased from 1721 to 6031 for 37Cl, and from 7496 to 9664 for 35Cl, with a greater range of rotational quantum numbers than found in a previous study. A total number of 1457, 484 and 262 line assignments were made for 20 1911, 70 191 1 and 20 161 1 hotbands respectively, features otherwise completely obscured in the observed spectrum. Rotational and centrifugal distortion parameters were fitted for all the upper states.