In my Convenience Center there is a sticker that gives instructions for both methods, so Keystone must approve both methods. I've been told that rigs leave the factory having been winterized by the blow-out method.
My instructions say that you must blow-out the Black Tank Flush with either method, so while the compressor is out, I do all the lines before pumping in the anti-freeze.
There is too much I can forget with the blow-out method by itself, like remembering to run the water pump for 30 seconds after it's dry.
Jim & Martha Abernathy
2014 Montana 3402RL Level UP, Sailun S637's, TST 507, Renergy 100W solar
2014 Ram 3500 Laramie® 4x2 diesel dually crew-cab 3.73 axle, Reese R20