Details of the model and algorithm can be found in the paper Idiosyncratic Risk, Aggregate Risk, and the Welfare Effects of Social Security, published in IER in 2019 joint with Alexander Ludwig.
The outer solution routine for aggregate risk is a variant of the Krusell-Smith algorithm.
Harenberg, D., & Ludwig, A. (2019). Idiosyncratic Risk, Aggregate Risk, and the Welfare Effects of Social Security. International Economic Review, 60(2), 661–692.
DOI: https://doi.org/10.1111/iere.12365