Familiar with WhatsApp, VMware and android emulator such as bluestacks. Use one VM to hold one emulator. Install the WhatsApp and open one account in the emulator and use Arificial intelligence tool such as autoit to perform some task. Then use the WhatsApp local database to communicate with other whatsApp user. Since there are a lot of whatsapp accounts, the control of on and off of each VM is necessary.
A control panel to perform the database administration is required.