"There's more than one way to skin a cat."
And there is apparently more than one way to apply an Unna Boot. Which one is right? Probably the way the physician who ordered it wants it done. So best to check if they have a preference. If they have no preference, do what makes the most sense to you.
Most of the unna boots I have applied over the years have been for wounds that are chronic, non-healing and usually because of venous insufficiency. Rarely have I seen it ordered just for edema. Too many other easier options to use.
I remember years ago a podiatrist happen to visit patient while I was applying an unna boot. She watched as I carefully applied it, no wrinkles, 50% overlap, cutting the wrap and repositioning the angle so as to continue up the leg.... until I reach about halfway up the leg. Then she grabbed the roll right out of my hands and wrapped that sucker willy nilly, telling me it didn't matter. None of it mattered. Just get it on and covered.
Well, all righty now!
I would say that about the only thing that troubles me with any of the variations is wrapping from the top down to the toes. It goes against everything I was taught about compression applied to the limbs having to go from distal to proximal position. So I would avoid it.
Some people use cast padding as a second layer. I never did because, well, we never had any. My agencies used kerlix which accomplished the same thing.
Remember to have the patient flex his foot so that after you wrap, it will be possible for them to stand and walk with the dressing on.
This boot needs to be kept dry and can stay on up to a week if there are no wounds underneath that produce drainage requiring change sooner.
It is also important to remember that since the boot is moist, the skin will be as well and therefore more fragile than normal. Cutting off the outer layer (Coban) is fine, and if you are careful, cutting off the kerlix is appropriate. But if you try to push that bandage scissor under the actual unna boot layer you can accidentally cut the skin.
There are two basic types of bandage scissors you can buy. The first is smooth with rounded edges and less likely to cause trauma or a laceration to the skin if held at an angle.