Marque,

Hopefully this will answer your question.
I'm using PS 7

1. Create your new brush.
2. Go to "Edit" then "Define New Brush"
3. Agree with or rename your brush
4. Click Okay
5. In the upper right hand corner of the Brush Pallete, click on the arrow and select "Save Brushes"
6. Rename them if you want and choose "Okay"

This will add the brush to the brush pallete you are currently using.

To get it in it's own pallete, I do something that is awkward.
Someone else might have the proper way of doing this. But what I do is first select a brush pallete that only has a brush or two. Then I follow steps 1-4.
After this I delete the unnecessary brushes.

1. Simply "right click" on the unnecessary brush in the pallete and chose "delete brush."
2. Follow steps 5-6

You can rename brush palletes by:

1. Clicking on the "arrow" in the upper right corner in the "brush Pallete" and choosing from drop down menu "Rename Brushes"
2. The easy way is to just rename them as you save them.

hope this helps.

I'm not too sure what you are asking in your 2nd question but maybe this will help.

If I make a selection in a picture in PS what happens when I inverse the selection is that I choose everything except the item I chosed.
If you have nothing that is in the background, if you inverse the selection then you chose nothing.
If this is what you are doing and you want to select an item that is alone on it's seperate layer then do this in PS7:
1.Select that layer
2.Hold down the "Ctrl" button (PC) and with that button held down "left click" on the name of the layer in the "layer pallete"

That will select that object.
This may not be what you were asking but maybe it will help you in the future.

take care