Brett generally does not create acidity. If you get acidity from brett then it is primarily acetic acid from excessive oxygen exposure. Your goal with brett generally should not be to create acidity.If you're looking to introduce a small amount of acidity an easy way to do that is to add brett to your beer and give it months to mature. When you are happy with the brett character, brew a small kettle sour version of the same beer and blend the kettle sour into the brett beer. Then package.