Multiple build machines

I forgot to address your very first question

Yes, it is possible to hook up multiple build agents to the drone server. If you look at the official installation documentation you will see the agent configuration, using docker-compose. You provide the agent with your drone server address and shared secret:

  drone-agent:
    image: drone/drone:0.7
    command: agent
    restart: always
    depends_on:
      - drone-server
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    environment:
+     - DRONE_SERVER=ws://<server>/ws/broker
      - DRONE_SECRET=<secret>

You can start as many agent containers as you want on as many machines as you want. All you need to do is make sure they have the correct server address and secret.