My knee jerk reaction is to avoid any kind of lubricant on the sear that will attract debris, but my reason would be for the abrasives attracted might accelerate wear on critical components.
If I were to choose a lube for something like a sear, I'd choose graphite. And a pencil will lay a nice surface of it. Unlikely to absorb problematic contaminants.
As to wax as a lube, my primary concern would be that it wipes away and won't find it's way back. Liquid oils will work themselves into contacting surfaces. Even if they get pushed out, they get back in- "surface tension" effect. Some tacky greases will tend to work their way in too, but I would guess not the best choice for most firearm uses. There are a few though- like the bolt roller in an m1a for instance takes grease.
I'm not describing this as well as I'd like, but a good demonstration is try and lube a door hinge with wax, then try oil.