How can I make hunting Khezu quicker?

In general if you want to make hunting faster you could always use pitfalls (ivy+spiderweb + traptool) or/and shock traps (traptool + thunderbug or genprey fang). you can always use multiple and bring to combine more (note that each time the monsters will last less in the traps, but you still get free hits on them). Also, make sure you are hitting him in his weakspot(head or where you see more blood). Also khezu will eat poison meat. While we are at it, you might as well buy large barrel bombs and use them while he is trapped, those deal a lot of damage.

Remember in this game items are VERY useful, dont forget you can use them.

And most of the time, the scent thing can be ignored, it might be useful when fighting in groups, but when you are alone it wont matter.

If you want to fight him when he goes to the ceiling, that might be hard, bounce bombs do very little damage, and while you might get him down once, it might not be enough. Also, setting the bounce bombs might make you vulnerable to his saliva. Your safest bet is just get away from his shadow and wait for him to get down.

Dont worry, this is a long boring fight with melee weapons. Bows would be useful to get him down, but make you vulnerable to his electric attacks. Thats why I recommend setting traps and making the fight on ground longer.