You can do it with mercury, or you can do the Becquerel process - the Becquerel process involves no developing chemical, but instead the plate is re-exposed to full-spectrum light through a sheet of rubylith. You have to change your sensitization process if you plan to do Becquerel development. There are a number of books out there that have an extensive description of the process - the Christopher James book and "Coming Into Focus" by John Barnier are both good references.
You may find this eight-and-a-half minute video interesting.
"When making a portrait, my approach is quite the same as when I am portraying a rock. I do not wish to impose my personality upon the sitter, but, keeping myself open to receive reactions from his own special ego, record this with nothing added: except of course when I am working professionally, when money enters in,—then for a price, I become a liar..."
— Edward Weston, Daybooks, Vol. II, February 2, 1932
There are two alternatives to using hot mercury. The "Cold Mercury" method uses mercury at room temperature in a vacuum. It was developed in the 1980s or 90s by John Hurlock. The other method is the Becquerel, mentioned in a few 19th century texts, which uses a red or orange light to develop the plate. Lots of details at http://www.cdags.org/ or a brief summary of my Becquerrel process here: http://www.alternativephotography.co...-daguerreotype
And yes, it is a painfully difficult, expensive, and unpredictable process, but the results are worth it...
IIRC, a 4x5" plate by itself is about $40-$45 US. Not including the costs of the other chemistry and hardware required to do it safely - that stuff probably adds another $10-15 per plate. This is one reason I just collect originals now
YIPE! That's rather expensive. But worth it I suppose. Then again, I have NO experience in these things, so regular film or the stuff in a bottle would be a better starting place. That way, if I flub, I won't go bankrupt...