About the only thing you'll gain by polishing on the crank is to polish the port area under the carb. The rest is irrelevant because it rotates on a bearing and polishing the bearing mounting surfaces may actually cause the bearing to spin on the crank. As far as the rod goes, polishing probably won't help or hurt you. Be careful not to get it too hot polishing it because it's possible you might warp it. Knife edging is what you want to do. If I'm not mistaken your rod is already pretty well knife edged. I wouldn't recommend grinding on a rod to form a knife edge. I'd use a file and work slowly.