How can I edit GTK+3 themes (preferably with a GUI)?

(similar problem to one in a question I had before, but I need multiple solutions, and I felt they were better organized as separate questions)

Upgrading from 11.04 to 11.10 did away with my themes, without warning me. And I can't find any themes online. I'm not enjoying Ambiance, or Radiance, or any of the ones offered by default. I found a couple that I kind of like online, but they're not quite right. Instead of looking for somebody who coincidentally came up with the perfect theme for me, I'd like to find something close, and edit a few pieces to fit my tastes.

Particularly... I don't like gray. I get why sometimes you wand a bit less contrast, but most of the time, gray just makes me unhappy. So I want to give my theme much more contrast in colors, with perhaps some shade of blue where I feel actual color is necessary. These sorts of edits were simple enough back in 11.04. I can't find a way to make them in 11.10.

I can't seem to find any way to customize the themes. I really want to customize my themes. This is Ubuntu. I know I can. What's the simplest way for me to do it?

I copied a the theme from /usr/share/themes that is close to fit my needs to /home/user/.themes. After copying the folder I removed the settings for the window-managers that I don't use. Now I used that copy to edit the appearance of the theme.

I changed the gnome-shell.css file in the folder of the specific window-manager. (here gnome-shell folder of course) So far I played around with the size of the icons and their spacing in the application overview. The file itself has a few comments which hint to functionality and to the purpose of the parameters. Just look there and play around... if you mess it up just replace it by the original theme. Hope that at least leads into the right direction.