I've done the hacksaw blade thing, the corner/edge of various files, and 36 grit sandpaper on a sanding block, and they're better than nothing, but they don't leave behind the same quality surface as a properly sharpened toothing plane blade. Others tear, while the toothing plane cuts very cleanly. Does it matter? Maybe, maybe not. It probably depends on how critical the bond is. I feel the joint in my handle and dip area is critical, so I'm going to do it the best way I know how.
When prepping handle gluing surfaces in bows, I don't do the angle/cross hatch technique like he showed in that video, and since the mating surfaces are often deflex and reflex shaped, the blade is held by hand, not mounted in the plane. I hold it more like a cabinet scraper and run it parallel with the length of the work piece. The blade is sharpened on a very slight radius so that it's slightly convex when finished and leaves a slightly concave surface... and I mean slightly... a few thousandths. These techniques make for virtually invisible glue lines along the bow's edges.
If you watch, you can get a toothing plane blade, blade only, on ebay pretty reasonable. The last time, I got a package deal of 4 of them of various teeth per inch. I have 6 of them now