Confusing selections and masks

[pixelator]

I'm having trouble understanding the basics of masks and selections.

Here's an example of where I'm getting confused:
- I've opened up a color photo in Photoshop
- next I've created a new adjustment layer with the "black & white" function.
The photo has now turned into black/white (although I know that the bottom layer (the original photo) is still in color

I assume the topmost layer ("black/white" adjustment layer) is sort of like a black/white filter which covers the photo. What I want to do next is "cut holes" in the filter to allow the color photo to let its colors through in selected places.

painting back colors
Having selected the topmost (black/white) layer I choose the brush tool (B), set the background/foreground color to default (D), then choose black as the foreground color (X) and start "painting" the parts of the photo back in its original colors. If I paint too much back I press X again (to reverse the foreground/background colors) and erase with white. So far so good.

I've briefly learnt about the Quick-mask, and I know that selections are shown as "marching ants" around whatever is selected, so why isn't what I've just painted surrounded with marching ants? Haven't I just painted a selection?
Can't I combine this with the usual types of selecting stuff?

Selections not working
Moving on I expected to be able to select a part of the photo (e.g. using the "rectangular marquee" tool) on the "black & white" adjustment layer), then pressing backspace to delete that selection (i.e. making a hole through the black/white layer), but that does nothing -why?

 

[mfox]

What you need to do is add a layer mask to the Black and white layer, and use a black colored brush where you want color, You cannot select on "Adjustment layers" click on the color layer to select then make sure you click on the black and white layer and invert

here an example

 

[pixelator]

Thanks, but that's exactly what I've already done.
I do notice however that you have two masks in that layer -what does the second (rightmost) one do?

And what about those "marching ants" -why don't they show up when I paint using the paintbrush on a mask layer?

 

[mfox]

Thanks, but that's exactly what I've already done.
I do notice however that you have two masks in that layer -what does the second (rightmost) one do?

And what about those "marching ants" -why don't they show up when I paint using the paintbrush on a mask layer?

rightmost is adjustment layer mask; marching ants only show up when you have selected something on the picture go to the orgianl layer and use any selection tool then go back to the adjustment layer and paint or fill it on the layer mask