How much and how often exactly do you DCA?

I hear DCA all the time and I know what it is but exactly how much and how often? If you had $300K in sitting in cash, what percentage do you buy and how often do you by?

Is it a daily percentage or is it a time period you shoot for? Do you aim to buy in over a month? 3 months? 6 months?

Also, is there a way to set up to buy a certain number of shares at a certain interval with a brokerage without having to manually buy each day?

On a related note, rebalancing a portfolio. How much and over what time frame do you sell and buy into a new position?