Your method seems quite thorough. I'm not a fan of VI personally but I accept someone skilled in it could get quite accurate. That aside its maybe a little on the analytical side for typing on the fly. Is there a method you use when observing behavior?
You consider DCNH subtype in your initial typing?
It's not a bad starting point providing you don't place too much weight on it, in typing I find everything needs to fit into place. Just tonight I finally had that nice confirmation moment on my friends type (ESI), I typed him that weeks ago but I was only sure tonight because of his ignoring function of all things. Basically one of the things I've noticed about him and he noticed about himself is that he doesn't like socialising (Fe style) yet he does it effortlessly when he has to.
I think the type quirks will be a bigger benefit to me when I know more people of each type in order to pick up their quirks . So far I just know SEI's are overly fond of bath robes...and sleep.