2 cups water
1-3 tblspoons lemon juice
1 squirt Dawn
1 tblspoon salt
I used to use laundry detergent but found Dawn works better and is already dissolved. More lemon juice if it is oxidized brown "desert" brass. The brass will turn a redish color as the surface zinc is being leached leaving more copper exposed.
The neat thing is you've probably got these ingredients at home already. Don't forget to punch out your primers first to clean primer pocket and speed drying time.