A difficult verse should first be classified by the nature of its difficulty. Is the vocabulary unfamiliar? Has a word or clause been omitted? Is a pronoun reference uncertain? Or is historical context or a question about abrogation relevant to a legal statement?
Lexical problems call for word usage; syntactic ones for sentence structure and ellipsis; contextual ones for audience and circumstances; rhetorical ones for figures of speech and their signals.
Several causes can coexist in a single passage. A single interpretive technique is therefore not sufficient for all cases.