Áhi se va, “there it goes,” means “as it is.” The Diccionario del español de México of El Colegio de México gives the expression hacer algo al áhi se va and the example “Entrégalo, áhi se va” (Hand it in as it is). Hechizo describes something made improvisedly, without following the genuine rules or procedures, such as una turbina hechiza, a homemade turbine.
A ojo, or a ojo de buen cubero, “by the eye of a good cooper,” means by estimate, without measuring or weighing. The dictionary’s example is a kitchen exchange: “¿Cuánta cebolla le pongo? A ojo, según la cantidad de carne” (How much onion do I add? By eye, depending on the amount of meat). Al tanteo means by approximation, without a precise measure.