My now late parents did this with the assistance of a solicitor at the same time as they made their wills.
The house, their family home, was mortgage free at that point.
A deed of conveyance was drawn up and executed and then registered in the Registry of Deeds. This was circa 1999.
The deed transferred the property from just Dad's name to both his and Mam's, and the consideration (which I've since been told is pretty standard) was "natural love and affection".
On Dad's death the property automatically became Mam's as they co-owned it at that point as joint tenants.
The house did not form part of Dad's estate which was, I assume, the reason for doing it in the first place.
I would concur with the advice above that a solicitor's guidance would be best in this sort of instance.