Well... several things I've seen:
1) Get some AVID bearings. $1 each online. Great bearings. (There are other good ones too, that's just what I use.)
2) Blow the grease out of them with compressed air (there will be enough left to keep them lubricated) If you leave too much in there, it gets slung out into the clutch bell, causing slipping, and more heat.
3) Make sure your endplay is set right. You should be able to move the clutch bell front to rear slightly... it should spin freely without binding, but not be "sloppy." Maybe .25 mm of play.
4) Make sure your mesh isn't too tight. There should be slight play in the mesh with the spur gear. If run a strip of paper between them and tighten it down so it is tightly meshed, it should be about right when you remove the paper.
And the OFNA clutch bell is slightly different inside diameter than almost all the others... I can't remember if it is slightly larger or smaller... but if you run an OFNA bell, yes, use OFNA shoes. I personally like the Mugen flywheel, either Mugen or Dynamite shoes (the Dynamite ones last a lot longer) Mugen or Kyosho springs, and Mugen or Racer's Edge clutch bells. Team Cobra now has new clutch shoes that come with springs, but I haven't got to try them yet... they look like they'll be good though.