If you can tell us what systems you are using, what kind of invironment, I might be able to help, but I don't know of any sites that explain everything about chroma Keying. Just about every project has it's own little quirks that have to be overcome.
Don't use DV. As related by others much smarter than I in this very thread, DV is a bear to key. DV is a compressed format, and the part of the signal you need to make a good key is thrown away in the compression process.
I think you're hosed, between the DV and the shutter action, you might be trying to key one field's worth of image info in each of those motion frames. For the frames that are not working, You will need to hand-rotoscope those. You can export a frame movie into Photoshop, or use a paint program or compositor (hopefully with a wacom tablet and pen) to draw sharper mattes around the hand and finger, etc.
In DV, keying off green tends to work a little better than blue, as you have more luminance info with green. One other trick you might try is to do a luma key instead of a chrmakey, or combine the matte generated in luma over the chroma matte. Anything to avoid the tedious hand-roto work;-)