Yeah, I use the wet stuff. I have no experience with the dry version, I imagine it's the same, but....
Here's what I used, or the Rutland version...
http://www.amazon.com/MEECOS-1352-Furna ... ace+cementAs far as I know, it's sodium silicate mixed with high alumina clay, so when you add it to your fireclay you are giving the fireclay a boost of alumina and binding it all with the sodium silicate. You can get by with just adding sodium silicate to your fireclay/perlite for a cheaper version, but I can find this stuff at my hardware store and can handle the $15 cost of convenience. I use one quart tub for one stove, approximately. It's pretty forgiving with regards to ratios.