When you are bleeding your system, only have the pump plugged into your power supply. Use a paper clip to jump the green and black wires. This will ensure that if there's a leak in your system, it won't splash onto a vital component which will damage it on contact. That's very important.
Second, there's no way really to bleed the whole system at once, you have to fill the reservoir, turn the pump on, let the water level drop emptying the reservoir and then turn off the pump. You don't want air in the pump or no water because it will damage it within seconds. You'll just have to repeat the process filling the reservoir, and the turning on and off the pump till its all bled.
Third, if you want to drain your loop, get a t-line or y coupling and install it at the bottom of the case, run one set of tubing for regular circulation and from the other port in the t-line, run another short tube for draining.