Choose a question to test
You do not have to prototype the whole product at once. Start with the main journey: finding a service, choosing an option or making an enquiry. Define what the test should clarify, or the prototype risks becoming just another set of screens.
Distinguish working features from placeholders
A prototype may use sample data and simplified states. Make these clear to the team so that an attractive transition is not mistaken for a finished integration. A list of limitations helps everyone assess the remaining work honestly.
Record decisions
After the discussion, write down which journey was chosen and why. Separate feedback from new ideas for later. This preserves the purpose of prototyping: reducing uncertainty instead of endlessly adding possibilities.