The "acid first" protocol is championed by Dana Johnson at Birko. He's got papers published that explain the chemistry. I think you could google it to read them. I've tried it and it does seem to remove beerstone more effectively. I don't practice it now because I find that the using the acid after the caustic removes the tenacious caustic more effectively than just water rinsing the caustic. Or non-caustic alkaline detergents, too. But there are many ways to clean a tank and there are many factors. I do not use an alkaline wash on our 12 serving tanks in a cold room. Instead, I use an acid detergent designed for cold cleaning in a pressurized CO2 environment. Saves time, CO2, energy, chemicals, and water. And I only caustic wash the mash tun a few times a year. Otherwise my mash tun is hand cleaned every brew day and stays clean and bright without the need for chemicals. Kettle also comes clean easy enough with a quick brushing, although I do chemically clean it every 3-5 batches. Fermenters are where I stay old school and caustic-rinse-acid-rinse-sanitize every time I use them. Always like to hear what else might work elsewhere! Let us know what your experiences are with this system if you decide to give it a try. Cheers!
Palau Brewing Company