ahhhhh, C4Ds and gradient maps are practically found in every single one of my graphics now, lol
I recently downloaded a bunch of new gradients yesterday, too xD
C4Ds are pretty easy to place, honestly, or maybe that's because I've been using them for a long time . . . they can work as background, shapes, lines, and even accentuate the flow.
The fact that they're so multi-purposeful is the reason I love using them, along with pentooling xD
And I prefer GIMP over PShop, so of course that's what I use ^^
I've been trying to replace my version (2.6) with 2.8, though, but my stupid desktop won't let me -_-
Clipping masks are really easy to make. Basically, in GIMP, there are two ways: the layer mask way, and the "other" way.
I use the other way the most, because it's real easy.
1) Layer > New from Visible. After you get your visible layer, you can move/flip/distort it any way you want.
2) Hide the Visible layer, and create a new transparent layer.
3) Brush on the transparent layer
4) Then right click on the brushed layer, click on 'Alpha to Selection', and hit the delete key.
5) You should still have the "marching ants" on the layer, even though you deleted the brush marks.
6) Click on the Visible layer, and unhide it, making sure that the selection of the brush marks is still there.
7) Select > Invert, and hit the delete key again.
8) Ta-da! You should have a clipping mask~