I have used an EasiYo for years. It is very, very easy.
We make a batch at least twice a week using the easiyo sachets of milk powder and starter.
Mix powder and cold water in inner container, and put inside outer insulated container of hot water.
We make it in the evening, ready by morning
We like it because we eat it fresh while it is still mild. The longer you leave it, the stronger it tastes.
I used to make Yog in a wide-necked flask, using a spoonful of the last batch, but wouldn't go back to that.
We live too far from a supermarket where we could get equivalent quality, so it makes economic sense.
Apart from anything else, it is easier to get the powder delivered than haul milk from the shops.
We get ours from Lakeland - Greek style natural (avoid the low fat version!)
PS. You could probably use the easiyo containers to make yog with milk and a spoon of live yogurt, but it would take a bit of trial and error to get it right.