You can not use water over bare bondo or metal as it will start to rust. You can use water over epoxy primer, paint etc. After you have final sanded the panel and are ready to paint, wash with soap and water then let dry. Mask the panel as needed and then wipe it down with Final Clean(DoPont #3901) and a soft towel. We use blue paper shop towels from the auto parts store. Then use a good tack rag and final wipe the panel. You really should spray a sealer before you base to help keep the solvents from attacking the substrate. You are now ready to spray your base. Don't hose the base on, use medium coats and you should do just fine. Be sure to let each coat flash completely or you will have problems. Be sure your spray area is clean and blow yourself off real good before spraying.