The two bucket method is no rocket science,......its pretty simple.
First take two CLEAN buckets. Read the instructions on your car wash and add the amount of car wash concentrate mentioned, not less as you need the lubrication of the wash to safely remove dirt, dust etc. If you have a hose use pressure in the bucket to make foam and mix the wash with your hand. Use the recommended amount of water. In the next bucket pour only water. Wet your car with water hose. After dipping the wash mitt in the car wash bucket (squeeze it slightly to remove excess wash), wash a few panels....say a fender and two doors. Then dip the wash mitt into the clean water bucket to rinse it so as to remove stuck up dirt particles from the mitt. This is necessary if you don't want the mitt to scratch your car. Then after squeezing most of the water out dip the mitt into the wash solution and move onto the next panel.
*You may need to change the water of rinsing bucket if your car is really dirty.