Cob isn't concrete. It is a composite material. I have been told by long term cobbers that the more straw you put in the better. The straw binds it and will allow it to settle over hundreds of years without cracking.
And I beg to differ about the tarp method.
It is a lot more work than mixing in the barrow and at the end of the job, you have to pick the stuff up off the ground to get it to where you want it.
I have done cob by tarp and by wheelbarrow so I have the benefit of experience.
Tarp mixing is a lot more work and it takes longer too.
It is great if you can get a bunch of volunteers to do the mixing. But if you cannot, then you need to use the least effort possible. And the wheelbarrow comes close to that. If your clay is well soaked before it goes into the wheelbarrow, or if the clay is mixed with a heavy drill and mixer attachment, it is even quicker.
About 2.5 cubic ft per mix, 6 mixes per hour, comes to about half a cubic yard per hour. Thats a lot of cob.
Brian

I am from Co. Carlow. Now I live in Canada
There are still clay houses in Wexford and my mum used to live in one when she was younger. My uncle also had a clay house.
It is not a job for this time of year! I think the main thing now is to find good clay.
You need to start cobbing in decent weather and probably in Ireland it needs to be finished before the start of September because it has to dry out before the first heavy frost.
I only have barley straw available here. You will have wheat straw available and maybe rye straw. I think rye straw might be best.
I think some people have built Cob houses in Ireland too but I have not been back in ages. You could make contact and see what they are doing.
I am also interested in light clay construction. Basically they mix straw and wet clay (with only a little sand) and then use it as "infill" in the walls.
AND, as far as I know, it is in the building code in parts of Germany!
I have a link in the video introduction on utube.
This probably uses a lot less material than cob and has more insulation value. In Ireland I think the more insulation, the better.
I hope you go ahead with your project. I imagine that simple cob sheep houses would be super useful in winter in Ireland.
But I doubt that farmers will make them unless they see that it can be done.