We never use one method and always combine different instruments and techniques.
For example, our favorite method is combining BPMN and CJM. We often create new visualization of the information we receive during the research because our main goal is to convey research results in the most clean and precise way and not to fill the data into a template that rather hinders the perception.
We use all currently existing product instruments: Lean Startup, Customer Development, Design Thinking. Frameworks: Customer Journey Map, Jobs to be done, Personas, Perceptual Map, Value Proposition Canvas.