A U-shaped production line is considered one of the most flexible designs used by companies to adapt to varying production conditions and to implement lean concepts. Similarly, work-sharing allows for cross-training of a flexible workforce while achieving high levels of worker utilization. This paper proposes a new protocol for U-shaped assembly lines that relies on work-sharing principles and on an adaptation of bucket brigades to cellular environments. Discrete event simulation is used to maximize throughput while determining buffer locations and buffer levels for each worker. This model is validated with a physical simulation and then tested with industry data. The results show the protocol enables a high level of throughput and worker utilization for the manufacturing cell while capping the maximum amount of WIP in the system. The proposed protocol is generalizable with respect to the number of stations, processing times, types of processes, and worker velocities.