were you ever able to find any videos for how to use the Knife tip properly? I'm about to buy a Hakko 951 and was considering a knife tip, but not sure how that might be helpful.
Pros and cons of the knife tip.
Good at loading solder
Good for drag soldering
Can be used to remove solder bridges
Can do some precision work
Good thermal mass
Works well in straight lines with PCB space
The tip is pointy but it's not so useful for poking holes
Using the very tip to solder through hole is not the best
Can be used for tinning wire
Can be used to desolder and wipe pads
Can be used to remove some surface mount components from the PCB
Better than most at soldering heatsinks but not as good as a high mass chisel.
So it's not really the best tip in all situations but more a good all round tip. A specific sized chisel for through hole, a pointy one for very fine work, a purpose specific drag soldering tip etc, will all do their job better.
If you are only ever going to buy one tip perhaps. I'm still really fond of the chisel at least for 90% of soldering individual pads.