This potato grater works well to get the mushrooms into smaller bits:
https://www.amazon.com/gp/product/B0000VLV6Q/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B0000VLV6Q/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1