Turn photo background to B&W

This is a really nice effect that I picked up in this PolishLinux blog post. However, I have to admit that I just couldn't follow this guide. In step 1 he says to duplicate the background layer. Well, I could see how to duplicate "a" layer but not specifically the background layer.
Also, the dialog box that he shows in this step I just could not find.
Nevertheless, I did very much like the effect and went about it in my own amateur way. As you can see from the pictures, however, it actually turned out very well.
Here's what I did:
1. Fire up the Gimp (I'm using Gimp 2.6) and open the photo you want to alter with File>>Open
2. Now go to Tools>>SelectionTools>>Free Select
3. This is the hard part; use the mouse to outline as carefully as you can the object (or selection of objects) that you want to stay coloured. Note that it's very important that the tool line completes a loop. In other words, it's got to finish exactly at the point from where it started. This ensures that you have created a fully enclosed space. Therefore make sure you remember wher you started from as failure to do so can lead to some frustration.
4. At this point, just to get your coloured object to stand out even more, you might want to consider sharpening this part of the image. You can do this by going to
Filters>>Enhance>>Sharpen
I found that sharpness values in excess of 75-80% start to give ugly, excessively distorted images so I generally chose 75%
5. Next go to
Select>>Invert to focus on the part of the image you want in monochrome.
6. Finally go to
Colors>>Desaturate
I always chose Lightness and then OK.
7. Next save your file.
Almost certainly you won't be able to do this in just one shot, so save this first attempt under a different name and open this new photo in Gimp.
Now use exactly the same procedure to continue touching up the shot.

Possibly this sounds over-complicated but to put some perspective on this, the changes seen the shots I appended here took no more than 10 minutes in total.