Unclear requirements become easier when they are converted into a sequence of decisions.
Start with the business purpose
Before choosing tools or sources, understand what the final information will be used for. This changes what should qualify and what can be excluded.
Break the requirement into layers
I separate definitions, inclusion criteria, exclusions, source priority, validation rules and borderline decisions. Then I test a small sample before scaling execution.
Complexity reduces when ambiguity is converted into a process.
Standardize only after validation
A workflow should not become an SOP simply because it looks logical. First test whether it produces the right records. Then standardize it so the team can repeat the judgement consistently.