I don't know if this helps anyone, but I tend to think one application of the Blend skill as being applicable when the enemies are not active. Whereas Sneak, is when the enemies has been alerted already, or are deliberately watching out for something.
Being disguised as an enemy soldier and trying to avoid drawing attention to oneself while traveling with the army is
Blend.
When the army stops for the night, and you try to leave while everyone is asleep you use
Sneak.
When the sentry spots you and asks: "Where are you going?" you respond with a
Bluff.
Blend is sneaking in plain sight.
To use another Star Wars Example, in A New Hope, when Han and Luke are disguised as stormtroopers and walking around the Death Star, specifically when they shake deny the officer from getting in the turbolift with Chewbacca they are using
Blend. When they are asked "Where are you taking this
thing?" and after the shootout when Han is talking about reactor leaks on the intercom these are example of a failed
Bluff check. When they get out of the Storm Trooper outfits, and are going around the Death Star in their plain clothes (where did they keep their boots?) and avoiding patrols that is
Sneak.
Example number 3: When a hunter is just walking through the woods, searching for a rabbit, and dressed in camouflage, but trying to not to alert anything that would be a
Blend.
When the hunter finally gets close and the rabbit sort of perks up it's ears, the hunter has to start making
Sneak checks.
When the rabbit starts trying to tell you it's actually duck season, that's a
Bluff check.
Carousing a fancy ball for information when you don't have an invitation and not getting kicked out is a
Blend check.
Convincing the Duke of Farnigal that you are the 7th heir of the Royal line is a Bluff check.
Having a quiet rendezvous with the Dukes daughter in the room next to the party is a
Sneak check. I'm sure you could argue that other skills could be used, but this is a pg board.

When you're caught
in flagrante delicto and have to jump out the window that would be an
Athletics and
Acrobatics check.
Solid Snake hidden in a box =
BlendSolid Snake avoiding the guards after being notices =
StealthSolid Snake using the Ketchup Bottle as blood =
BluffSolid Snake removing the cigarettes from wherever they were hidden =
ResolveHopefully my interpretative examples help out.