There was a time, back when these bikes were fairly new, when you could actually purchase an aftermarket lightened flywheel. Lots of people put them on their bikes, and it greatly increased their ability to hit the shifts correctly. Then there were the rest of us who just learned the preload concept, worked at it and got to the point where we were able to shift fairly quickly and reliably, without sounding like we were grinding coffee, or banging the hell out of the tranny.
2 things I have always found useful is to preload, and use the throttle well. i.e. shift well above 3000 RPM. These bikes love to rev and hate to be lugged.