From what I remember from class, you are correct. The flash rate depends on resistance, and because LED's are much more efficient the resistors help to simulate an incondecent bulb.
What size resistor is a question I can't answer, but if you look at other ads for LED's I'm sure they'll name the size.
Yep. You need a resistor on every light to prevent the fast flash.
What? No flash relays on the VFR? If there is that would be the easiest as you wouldn't need all the resistors.
You can buy electronic flash relays (no resistors needed) that plug right in to your stock connection (http://www.customdynamics.com) or there are even flasher relays that you can buy at local auto parts stores (usually for around $5) that work as well. I just can't remember right now what type...
Vanion this is on my cb1000r. I think the built in flash relay is for incandescent and so is not the correct resistance as said above.
Correct. What I am saying is there are after market flash relays you can install in place of the stock one. This way it doesn't matter if the bulb is LED or incandescent. The flash is controlled by the relay irregardless of resistance. Therefor no more resistors needed and you can upgrade to LED's at your leisure and not have to deal with inline resistors any more.
Just go to the link apexandy has above to see what I am talking about.
get the LED flashers ... those Resistors get pretty hot! - what a waste of energy