Yoghurt propagation or yoghurt made with yoghurt

I’ve been making yoghurt with the Anova for the family for years and it only takes about 40 minutes to get 5 L (10 500-mL jars) into the SV bath for an 8 hour ferment, once a week. Stock pot on the stove, heat the milk to 190F, hold it there for 10 minutes to denature some protein for a thicker creamier yoghurt, stir in a cup of dry skim milk powder, cool in cold water in the sink to 109F, mix in 4 heaping spoons of yoghurt from the previous batch, use a measuring cup to pour into jars, slip into the SV bath, into the fridge after 8 hours, and enjoy the next day. Lovely, thick creamy mild yoghurt that barely lasts the week between the 3 of us. Easy peasy with the SV.

I’ll chime in here. I notice that most everyone is using individual bottles for their yogurt.
I leave out that step.
I heat the milk to 180-185 F.
My pot holds about 1.1 gallons or 5 quarts of milk. It also has the handles high enough on the pot so that I can suspend my pot in my souse vide container. A large square cambro container from the restaurant supply store.
I have my Anova waiting in room temp water while I heat the milk.
Once the milk is ready, I set the whole pot in the water bath and turn on the Anova.
While continually stirring, the pot cools off in the water while the anova is heating and circulating the water.
In about the same amount of time it takes to ice bath the pot, the water in the souse vide container is up to 111 degrees and the milk inside the pot is down to 112-115 degrees.
In the mean time, my yogurt from a previous batch is warming on the counter while I was heating and cooling the milk.
Once the pot is at temp, I stir in my cultures.
Simple, easy, and saves several steps.
Then it’s just an 8-9 hour “cook” and I have a gallon+ of great yogurt.
After the 8-9 hour cook, I found letting the yogurt sit in the refer for 12-24 hours makes it firmer.
I again don’t cool the pot before putting it in the fridge, since I have a second fridge, I set that cooler and use it for cooling the yogurt.
I also bought a yogurt strainer to make “greek style” yogurt.
After straining, I just store it in a large glass or plastic container with a good lid.
My family and I go through it in about 4-5 days, so I’m always making a lot.

As for the first batch of starter cultures, I went to cheesemaking.com and bought the Bulgarian Sweet culture. I just keep the rest of the packets in the far back of the freezer in case someone ate the container I save back for the next batch.