The layer menu should be attached to your GIMP window, at the bottom, as one of the tabs. If not, look at the bottom section, and click the arrow pointing left at the top right corner of the bottom section (below the boxes that show the foreground and background colors). Go to add tab -> layers. Yay!
If you cant see/the bottom section is missing, go to the top of the GIMP window, click file -> dialogs -> layers. And there it is. To attach to to the bottom, drag the word "layers" on the window to the bottom of the GIMP window where there is a tiny/skinny bar on the bottom.
Sorry if its confusing! I'll show you a screenshot if necessary :]
Hehe yes. I'm not sure how Color to Alpha works exactly, but what I like about this method is that you can draw under the lines and not affect the lines. Perhaps you may be able to do that with Color to Alpha as well, but I'm not familiar with that method. I think I'll investigate! ^^
Nice tut. I saw somewhere something similar, but instead of desaturating the pattern there was used "Color to alpha" function. I think it's better, because only the black stripes will remain and the white ones won't lighten your background.