@tsarstepan,
Several people.
Mother at times was able to convey and teach, other times she was a child herself and would be gnawing on a hand held lamb chop. I never knew what to expect from her.
Jerome and Irene were good at it. Jerome more so than Irene. He told me early on to watch and follow what he was doing with the utensils, glass, napkin, etc. With me and their grandchildren, an error meant being sent from the table to the next room to sit on a straight back chair- silently. This was Jerome's method, Irene would usually sigh and shake her head.
The locals (aunt and uncle in one place, grandmother in another) were sending opposing signals. The aunt was fanatical, and you did not wish to make a mistake in her presence, my uncle was strict but would allow some leeway, followed after cleanup by a lecture.
My grandmother didn't go for heavy etiquette- she knew the basics and was good in public settings but in her home meals were consumed by balancing a plate on the lap as her table was piled high with things. The glass or cup with a beverage was place on the floor. Often her cat would come by and take a sniff of the beverage.
My recently deceased brother went through phases. The first involved swatting the back of my head each time I made a mistake. Another was a school project for him (he was in college by then) and he observed and made notes which he then read to me while telling me what I had done wrong and how to correct it. I learned quickly in his third attempt when he used the reward system and gave me a whole quarter if I got through a meal with out messing up.
I know the basics to this day, including how to cut the flesh off a chicken and to do so neatly. I follow the rules in public settings and with people who I am not as familiar with. If it's someone I am comfortable with, formality usually goes towards the window although rarely exits entirely.