So for standard resin lustres I use the dry method.  Resin, salts, heat. For experimental lustres, like a silver lustre I've been working on, I've found the wet method to work best.  Carbonic acid, salts, precipitated as a soap in sodium hydroxide, and then dissolved in an appropriate solvent.  Depending on the carbonic acid used, usually isopropyl, toluene or turpentine. I've found the soaped lustres to be more reliable at lower temperatures, so that's why they work well with silver.