Bart,
My understanding of frost damage is that the moisture in the air condenses on the plants and when the temp drops low enough frost forms on the dew as well as in the plant tissues that are exposed to said moisture. A thin blanket or row cover (that was the word you were seeking) draped and secured with clothes pins should be enough to shield the buds from damage, without damaging the delicate buds.
Here in New England apple farmers also use large fans to move the air on nights when frost might hit the apples. That won't work for you, since you said there was no electricity out there, but it might for others who have a similar problem.
Good luck with your Wisteria- they really are stunning. Your English is great too by the way! Way better than my Italian 😉
