The problem is that everyone got intoxicated by the way patdavid builds the masks. His way is very pedagogic, but in real life you don't need to construct the masks by add/substracing/intersecting them(*). You can get your mask directly by applying the adequate curve to the B&W image (aka the "L" mask). This is much faster since you create a single mask directly.
Another shortcoming of following the tutorial is that you end up creating all the masks at once for the initial state of the image (and since this takes some time, and produces a lot of masks, you do it only once). But once you have worked on the image, some pixels may have acquired a new luminosity which is somewhat more (or somewhat less) impacted than their initial luminosity by another mask in the following adjustments.
Which is why I wrote ofn-luminosity-masks that uses Curves to generate arbitrary masks. It will quickly generate one given mask for the current layer. It comes with a bunch of presets (patdavid's masks) but you can add your own, and it also makes it easy to create a mask on the fly by generating a channel from the current layer, on which you can apply any arbitrary curve to select the luminosity range you want.
(*) a clue is the "M" mask, which doesn't select anything fully (max selection level is 50%).
Another shortcoming of following the tutorial is that you end up creating all the masks at once for the initial state of the image (and since this takes some time, and produces a lot of masks, you do it only once). But once you have worked on the image, some pixels may have acquired a new luminosity which is somewhat more (or somewhat less) impacted than their initial luminosity by another mask in the following adjustments.
Which is why I wrote ofn-luminosity-masks that uses Curves to generate arbitrary masks. It will quickly generate one given mask for the current layer. It comes with a bunch of presets (patdavid's masks) but you can add your own, and it also makes it easy to create a mask on the fly by generating a channel from the current layer, on which you can apply any arbitrary curve to select the luminosity range you want.
(*) a clue is the "M" mask, which doesn't select anything fully (max selection level is 50%).