Fill the tank with water. Some people prefer to premix one gallon of hot water with the product they intend to use, and then mix it with cold water supplied by a garden hose in the tank. This allows the powdered cleaning product to melt and break down a lot faster. It is essential that the product is adaquately mixed in the chemical tank.
Another tip to get an excellent mix? Briefly stick the end of your pressure washer in the bucket and use it like a blender to do a final mix of the product. The powerful agitation this provides will help break down any additional, stubborn powder.
Another important tip is to keep the tank elevated above the pump. This will allow gravity to assist you when using the tank kit, allowing what is a fairly low powered pump to reach 3 stories in height.
Make sure that the end of the garden hose coming out of your transfer pump has no nozzle attached at the end. This helps to create suction that will get water moving through the pump without assistance.
Open the choke on your transfer pump. Pull start the pump three times without turning it on. This helps fuel move through the pump. Wait two minutes, and then turn it on. Open the choke a little.
It should start on the first pull.
Spray chemicals from the roof line and you should get great coverage from even a small pump.