I have one question. Just don't kill me over it.
Socionics people jump every time someone even mentions MBTI. Yet, there is a remarkable similarity between the two. The type can't always be simply converted from one to another, but very often it can. Let's leave the j/p issue out of the question right now. People don't even know themselves which one they are, so it would be arrogant to think that I would be able to type this letter correctly when typing my friends.
I could call this "letter by letter" method, because I don't know any official name to it. This could look like that: ...He is definitely not extroverted. He's very reserved and kinda shy. That means "I". He seems to always know what's going on in his surroundings. He's quick to react, very adaptable and practical. I would say "S". He's very touchy-feely, especially for a guy. Also he's very considerate of the feelings of others and passionate about many issues. Sometimes just won't listen to reason and logic. All that together makes him an "F".... If he is clearly either j or p, then the type can be double-checked by reading the description. If not, then both descriptions (ISFp and ISFj) must be evaluated to determine the type.
Is it really so wrong to type people with the "letter by letter" method? The alternative method is the socionics method -> determine the type by the functions they use and check with the descriptions.