The Radar Echo Telescope for Cosmic Rays (RET-CR) is a pathfinder experiment for a future neutrino telescope, using cosmic rays as an in-situ test beam. The buried radar system monitors for echoes off high-energy cosmic-ray-induced in-ice cascades. The RET signal and dataset are well suited to a sub-threshold analysis, with properties that can be exploited in a singular-value decomposition and machine-learning-assisted search. This work presents progress toward using these tools for a future sub-threshold analysis. As a first application, we present an analysis of background data demonstrating some of our analysis techniques.