Two bucket method, as the name implies, mean you use two buckets when washing the car. One bucket with your soap, the other just water. You use the bucket without the soap to clean off dirt from the sponge before dipping it back in your bucket with the soap. This greatly reduces the chance of you getting your soap water dirty, which would put swirls in your paint. Sometimes my water bucket will have so much dirt in it I cant see the bottom of the bucket (usually if its been raining for a week and havent been able to wash my car). Grit guards are another product great for reducing the chance you swirl your paint when washing. It is a grill that sits in the bottom of the bucket, an inch or two high, that lets the dirt particles settle to the bottom underneath the grill.
2005 BZJ GTO - Misfire and exhaust leak.