'Go-to' is commonly used to refer to a specific person, e.g. 'Smith is your go-to guy'. I haven't heard 'go-to' applied to a concept, e.g. 'a go-to foreign policy'. In the sentence 'go-to' refers to the example and not Mr. Smith. Word you are looking for is 'exemplar'--one that serves as a model or example. 'Mr. Smith is an exemplar as a parent.' It avoids the cringeworthy use of 'parenting', a regrettable practice of turning nouns into verbs. My answer may not offer an idiom but uses far fewer words than the original sentence. Only drawback is the hearer has probably never heard 'exemplar' in spoken English.
