You are right makers are like to have their own secrets =)
About "milking" ("molochinnya" how it calls here) it is quite open info here. But recently my friend started additionally to cover finished ceramics with special mixture "ganozis" made of wax and oils, probably this part he won't tell.
As for temperatures first firing is around 1000C and second not higher then 350-400C because if temperature will be higher the milk will burn out. As for clay - he uses bright one as image attached. If you wish I may ask him for certain sort
Milk should be "fat" that is why here was used milk of domestic cow, Usually domestic milk has more fat then one from a shop.
Here is some video of the process