We will present a real-life experience of using a MW-scale BESS with grid-following (GFL) and grid-forming (GFM) controls and a run of river (ROR) hydropower plant to achieve restoration of an islanded power system. To demonstrate this, power-hardware-in-the-loop experiments integrating an actual GFL/GFM BESS and a load bank are carried out. We will present both simulation and experimental results showing the different roles of BESS with GFL or GFM control in power system black start. These results provide further insights to system operators on how GFL or GFM controlled BESS can contribute to grid stability enhancement and how a ROR hydropower plant can be converted into a black start capable unit with the support of a BESS of relatively smaller capacity.