I love my seam ripper with the very thin, small, curved blade. It's actually designed to rip out serged seams, but works fantastically on small stitches. I've found it especially useful on the small stitches such as used when paper piecing.
As to the black on black, I'd recommend doing it right under an Ott light or some such and get every 3-4 stitches. Once you get a tiny area opened up, you'll be able to spread the seam apart somewhat and get to just the thread a bit easier.
Hope this helps.