I use graphite paint on my QA42 and it works great. I coat the inside of the auger housing and the inside of the discharge chute. I also remove the discharge chute and coat the area where it rotates to help prevent it from freezing up.
Did you clean up any rust and paint it before you used the graphite paint? If the surface was rough with rust the graphite paint will not work as well. You want a nice smooth surface. Also, I have heard that the brush on version has a higher content of graphite than the spray version. I use two coats of the brush on version and use the spray for occasional touch ups. This method has worked great in my experience.
I did a complete resto on my QA42A a few years ago too, sandblast, paint, bearings, etc. I brushed a few coats of graphite paint on the chute and a few other places. The reason for brushing is that I've tried the spray can graphite, didn't like it, didn't cover well, even after multiple coats. So, my experience is, forget the spray can. Graphite in combination with rubber flaps and a smaller pulley and the snow thrower throws snow further than I need it to. My other experience seems to be, with heavy wet snow, WOT is the best wat to keep the chute from clogging. My brain tells me that using spray cooking oil or WD40 or whatever, on the chute will only last a few seconds at best before it is worn away. One more thing, I brushed on multiple coats of graphite leaving each coat to dry overnight. I can't see through the graphite paint. It's easy to touch up in the Fall before the snow gets here again and, it's just become a part of the Fall maintenance check-up.