atDNA can most certainly help with that, but as you’ve found out nothing is automatic. If that person is a brickwall for you, then it's probably the same for others researching that line as well so you won't get any magic shakey leaves.
I assume by gg-grandparents you mean you know who the g-grandparent is. In that case, any cousins who match on the g-grandparent don't add much info (unless they’ve figured this out already), but they could be someone you can collaborate with. What you need are cousins who match on the gg-grandparent or further back who would be 3rd or more cousins. The problem now is the brickwall person is presumably blank on your tree as well as your cousin's tree, so ancestry's family tree match won't help. What you need to be looking for are surnames that aren't known to you that keep appearing in your matches, paying attention to the geographic location as well.
The response from MJ782 in the following thread describes one way of handling this:http://boards.ancestry.com/thread.aspx?mv=flat&m=691&...
And of course to state the obvious, for all this to work the cousins of value would already have to be tested and have a decent family tree that covers the line in question.
As far as my work, I'm still pretty new and also work full time (getting ready to head there now!), so I can't spend as much time as I like – especially with the recent flood of new matches. I haven't solved any specific problems, but I've found a number of confirmed matches. Although they didn't add any new information to my tree, they provided more evidence that the right people were in the right places, and they also gave me some new contacts.