Everyone has their own recipe for emulsions. I for one haven't tried double coating but I have found the Bergger COT320 to be more iffy to work with. The Arches Platine is more compatible with my technique. For what it is worth I find 0.5cc of emulsion is enough for a 4x5 and 1.3cc for an 8x10. I use pipettes - accurate to 0.1 ml to measure each solution and a syringe to spread the emulsion to a puddle pusher. For some negatives I might alter the emulsion but that's usually for contrast control. I prefer pt/pd with a tiny amount of gold chloride over single elements but to each his own.