I found this old Q/A after trying the tutorial referenced:
http://www.dslreports.com/forum/remark,15173919
Here is the full list of steps:
1)Open Image
2)Go to Image>Mode>Decompose
3)Check LAB, Check Decompose to Layers, hit OK
4)Open Layers dialog. Make only the B layer visible.
5)Duplicate B l
Quoting Colin Brace :
:
:
> 5)Duplicate B layer, set "B Copy" to overlay (Opacity is 100%).
> 6)Merge both B layers (Image>Merge Visible Layers/CTRL-M) Choose Expand as
> necessary (though other options don't make a difference in this case) Hit
> Ok.
> 7)Repeat steps #4 through #6 for the "A"
