I'd love to get some very subtle highlights, but can't afford to go to the salon right now.

I color my gray (I've done my own color for years) and I'm happy with the results, but from everything I read about highlights, they can be much trickier than overall color.

Has anyone done your own highlights at home? I've currently got level 6 neutral over about 75% gray (which is fairly resistant.) Ideally I'd love to get "caramel" highlights.

Any suggestions? Dire warnings?