This works for me on the releases. I used a combination of two or three microstock sites to create my newest release. I just packed it with legal language - sort of a melange of the most specific releases I could find. I made sure my releases have:
IStock's release is a good starting point, I think.
So my new release works for everybody (about 20 sites) EXCEPT DreamsTime.

So I have my models do a DreamsTime release and my new company release and that covers me for everyone.

Unfortunately my old releases often don't fly...so it means a lot of my "vintage" shoots (like last year) I can't use unless I can track down the model and get them to sign a new release. At microstock sales figures, I can't really offer to pay my models more...so mostly I'm just staying away from using models with my old releases. Bummer.

But then again, I do slide a few through...or add some missing info. A phone number seems to be the most often missed, but the easiest to track down. I never used to put the model's number on the releases. Nor did I have a witness sign. Now I always do.
Hope this helps add to Stockman's thoughts.
Cheers,
Scott/creatista