In the Oozaru Vegeta example, Vegeta's power was already greatly diminished by that point, as was stated, so it wouldn't be 18k times 10 but far less, and Krillin's power wasn't just 1200, it was supressed at that point. Nothing of this is really relevant, just wanted to clear it up.
SSJ Goku blocked SSJ Trunks's sword with his finger after he arrived on Earth. Slashing damage works like regular damage in DBZ world. Neither Freeza nor King Cold sure as hell couldn't have blocked Trunks's sword with their whole defense, much less their fingers. The power of the weapon is the same as the power of the user in DBZ world. It's just that the Ki Disc in particular has the property to cut through anything. Also, Kienzan (Ki disc) + Taiyoken (blinding move) combo would defeat any HxH character, though no DBZ character ever thought of doing that for some reason.
I also think the same holds true in HxH, though to a lesser extent. I doubt Tompa would be able to pierce Kuroro's Ren/Ken with Silva's Benz knife, for example, and Ubogin's skin broke Daltzorne's torture knife, and no syringes could be sticked into him.
Bullets coated with poison wouldn't work. They can't enter the DBZ characters skin, unless it's some sort of poison that enters through the pores of the skin or something.