Digging holes to concrete fence posts

Hello everyone, I am currently digging holes to set fence posts in concrete. I have spent about 7 hours for 12 holes so far. These are only about 30cm deep with a diameter of about 20cm. I still have about 25 more holes to dig. The soil is very clayey/rocky. I removed the top 10cm of topsoil with a spade and then finished the rest with a hammer and chisel. Does anyone perhaps have an idea how I can make this easier? I am concerned that I might destroy the drill bit of the earth auger because of the stones/rocks.

Earth auger and water the ground beforehand so that it is not too hard. The hand augers come in different sizes. This makes it quick.

PS:
With 30cm deep foundations you will not be happy. After the first winter everything will be crooked and slanted.
Frost-proof foundations are also recommended for fences.

I could try to get myself a manual earth auger. Would be an idea. Of course, I would like to go even deeper. But the way I went about it was basically impossible.

You have to make the holes wider, otherwise you won't come down properly. They should be at least 60cm deep.

You can manage that by hand, but just bit by bit.

The Fiskars earth auger works great here, even in clay.