I used a 12v rattle gun to take the flywheel off my old 900 when the sprag died, and I didn't need to use a holding tool when taking it off, just make sure you use impact sockets...
I've now got a plug in Clarke Impact Wrench after my old 12V one died trying to get 30 year old wheel nuts off my pickup and it's great ! Makes changing wheels, removing rusty suspension and caliper bolts a doddle.
From memory, it took 3 goes to get the right bits from Ducati though, each time getting slightly more expensive (and I may have put the flywheel back on wrong once as well which didn't help
)