Here's how I as an LII approach typing others:
My primary method is to see how how their functions are used according to model A. What appears to be their base function? Their creative function? Their PoLR? etc. I also take into account what quadra they best fit into and what their temperament is.
I find this to be me effective than taking a dichotomous approach (Are they more E or I? S or N? T or F? j or p?) although I will do this on occasion, when the first approach still leaves me with a few possibilities.
I do use a comparative method sometimes, where I look to see how the person resembles or differs from someone I know whom I'm certain of their type.
I don't place much emphasis on VI. I never use it alone to type someone. If I have it narrowed down to two types, I might suggest that the person VI's more like type X than type Y but it still doesn't definitively make them type X.
Test results don't mean that much. Just because someone says they test as a certain type doesn't mean they are that type or even close to it. The person may lack the self-awareness or may not understand the questions properly. Some of the tests are poorly written and even someone very self-aware with an understanding of the questions and what they mean could still get a wrong result.