Grist to the mill is a phrase that refers to something that is useful or beneficial to a particular situation or person. Synonyms for this phrase include "useful material," "helpful information," "a valuable resource," "a boon to," "beneficial," and "fruitful." Other potential phrases that could be used in place of "grist to the mill" include "a catalyst for success," "a contributor to progress," "a stepping stone," or "a springboard." Ultimately, the synonyms for grist to the mill suggest the idea of something that boosts productivity, aids in decision making, and brings about successful outcomes.