The protective speech seems to come with the structure: Brother(s)/Sister(s), since I (encountered a certain event), I do not recall intentionally (committing a certain unwholesome deed). Through this truth, may there be wellbeing for you.
I have tried to adhere to this structure, and to be as careful as I can in recalling past events and stating facts truthfully so I really hope it works. If you do decide to do something similar, thank you for being a kind and compassionate person.
As compassion (karuna) is a sobhana cetasika, according to Abhidhamma, it will invariably be associated with the universal sobhana cetasikas, some of which should at least bring happiness to one in body as well as mind. Do try it if you are inclined to.
When one cultivates a compassionate gati, then through the condition of repetition, kusala asankhaarika (unprompted) citta should arise more often in one’s daily thoughts. As these spontaneous thoughts have more merit and kammic power than kusala cittas that are prompted, one will be accumulating stronger wholesome kamma. This is my understanding. A positive cycle should then repeat continuously unless something drastic happens to change one’s gati.
I just read in a wisdomlib.org article about six pairs of universal sobhana cetasikas: passaddhi, lahuta, muduta, kammannata, pagunnata, ujukata depending on whether they pertain to kaya or citta. Here kaya does not seem to refer to the material body but seems to refer to the body of psychic factors, in other words cetasikas like vedana, sanna and sankhara, while citta refers to consciousness.
Some of these universal sobhana cetasikas help to cultivate meditations on brahmaviharas as well as to develop insight, for example, kaya-kammannata (wieldiness of cetasikas) and citta-kammannata (wieldiness of citta).
In fact, the universal sobhana cetasikas seem to suppress the five hindrances and some samyojanas (fetters) such as mana (conceit).
Thus I would think that cultivating these universal sobhana cetasikas through performing meritorious deeds indeed help set the stage for further development of concentration and insight.