Well the process is very easy. Take milk (I like to use whole raw but I've also used goat milk and standard pasturized). Add some fresh active yogurt. I usually make a half gallon at a time and a big tbsp is plenty. Mix it in and raise temp to 115. This activates whatever in the yogurt and begins to ferment the lactose in the milk.
Instructions online say to first raise the milk temp to 185 and then cool to 115. I did this years ago and quickly abandoned this step with no decrease in quality. The longer you hold at 115 the more lactose ferments and becomes lactic (acid and tart really). Store bought seems to have been only partially fermented. Online instructions say around 4 hours fermentation. I've experimented and really like the flavor and taste of a 24 hour fermentation. All the lactose is gone.
I have a dehydrator with a temp control. I can put the big glass bowl in at night and take it out the following night. Put it in the fridge to set and it is thick and creamy in the morning. I really like my dehydrator but dont want to plug commercial products on the open site. If you want to know which I use and why I like it PM me. I dont sell them or anything.
And incidentally, if you get a good dehydrator it is the shit for real. I don't know why more folks dont rave about them.