I thought I could do that, but I totally found out I couldn't.
Yeah, I've asked people and everybody told me
to just make a new layer, gradient it, and overlay it.
I did that, but it didn't work.
Do you see how her background is black and it isn't
"rainbow" colored.
Well, my background isn't really BLACK BLACK but it's dark
and I did the overlay thing, and only the background turned
colored.
Please someone tell me exactly how to do this.
Egh, I've tried this before with a white background
and my brush turned into the gradient colors
but the colors came out weird.

You don't make a new layer and do a gradient overay. For the brush layer, or the layer of whatever you want to have a gradient . You add a gradeint to that layer . By cliking the little "f" on the layer palete. Then choose gradient overlay. Choose the gradient. Set the option to "overaly" then click ok.

if you want something to be gradient and only itself press ctrl and then click on the layer whatever you want gradient then that the little lines will trace it.

use the gradient tool and that's what should happen..

sorrie if this doesn't help i'm not sure of what you're talking about :/

You can always just right click on the layer you want it on, Blending options-->Gradient Overlay then change the colors and levels around.

This is the EASIEST way:
-New layer
-fill with gradient
-set the blending mode to "MULTIPLY'