Actually, an impact wrench is good for removing it, but not putting it back. You need a torque wrench for that.
If you had it on the bike and had some way to put the brakes on, you could use the transmission to hold it. When I do it, I use my tool I made and then use a flat screwdriver wedged in between the crank and clutch basket gears to keep it from moving.
The main thing is that you need something to keep the engine stable.
If you are not in a hurry, I could come over some time with my tool. OR you could just buy one.
Clutch Tool
