Good luck! I have done a couple of marketing mailings to attorneys. I also followed up by phone on many of them, with zero return (out of over 100 letters and pamphlets). Apparently, they went right in the trash.
The attorneys in my area doing this type of work appear to have a corner on the market, so the number of estate and divorce attorneys getting the volume of the work is very limited. Try to find out who the largest firms are. A few of them admitted that they occasionally ordered appraisals, but they didn't send any my way. Maybe it's the old boy network, or just that the lawyers use someone with whom they are familiar. I don't know, but this is a hard nut to crack.
On the other hand, one local appraiser told me all his company does is attorney and estate work. He also mentioned that they get top dollar for these types of appraisals, so there is a market there; but getting into it is another story. :?