I have a 2017 Denali 280LBS and have been experimenting with the best practice for this as well. I have Ground Control 2.0 with the rear pinned extensions and I admittedly have not watched the DVD to provide instruction on this. l have some 4"x6" blocking to place beneath the feet for a couple reasons, first so the landing gear (front legs) don't have to be extended any more than necessary (the longer the extension the more unstable) and second, to provide more raise distance when the ground at the front legs is lower than the ground at the axles.
If on level-ish ground, I will extend the powered front legs 4-6 inches prior to manually dropping the pinned extensions. I do this because the telescoping powered part of the leg is more stable than the pinned extension part. This video says a rule of thumb is to drop the powered legs halfway to the ground prior to dropping the extensions (my interpretation - the feet should be halfway between the bottom of the trailer frame and the ground, or about 6-8 inches of drop).
I assume you also have the Ground Control 2.0 auto-level system if you have rear "drop-downs" (pinned extensions). After lowering the front pinned extensions to the nearest pin hole to the ground, likely each leg will be a different distance from the ground. I am still trying to understand the Ground Control system and haven't used the "Ground All Legs" function yet. So I run both legs down until the first leg touches the ground by using the "Front" button. Then lower the other leg alone by holding "front" and then immediately pressing the left or right button until the other leg contacts the ground. Then you can again use the "front" button to run both legs and lift the trailer off the truck.
Like I said, I'm still trying to figure out the best practice with Ground Control, but I have been manually running the front legs to a near-level position prior to hitting "Auto Level".
If the trailer is nose-low when you prepare to unhitch, you don't want to extend the powered legs very far prior to lowering the pinned extensions or else you may not have enough travel to raise the front to a level position.
If the trailer is nose-high, then you'll want to be sure to extend the powered legs 4-6 inches or more so you don't bottom-out the legs when you lower the front to a level position after unhitching.
Since I run the front legs to a near-level position prior to using Auto Level, the rear legs are less complicated because the height of the trailer is not going to significantly change when you use Auto Level. The rear legs, in their raised position, are lower and presumably more stable than the front legs in their raised position, so I have not been lowering the rear legs prior to dropping the pinned extensions. After dropping the pinned extensions, I use the "Ground Rear Legs" command. Then hit Auto Level and you're done.
I hope that helps and if anyone sees that I'm using Ground Control incorrectly please chime in.