You don’t do estimation without prioritization. As a consultant, my default way of working is kanban, often setup on Trello. Once I deconstructed the project in

You don’t do estimation without prioritization. As a consultant, my default way of working is kanban, often setup on Trello. Once I deconstructed the project into features, the first thing I do with the client is arrange them by priority and arrange them into sets for releases. If sales and marketing need to do planning, then they need to tell what they want to push back to the backlog so that the feature they want are on time.