You asked what coolant to use. Stick with the standard green ethylene glycol 50/50 mix with water.
If you don't want to install an overflow recovery tank, fill the radiator so that it covers the tops of the tubs - about 1 1/2" down from the tom of the tank. Don't worry if you over-fill it. When it heats up it will discharge the excess coolant out of the overflow tube and self-fill to its maximum when it cools down.
