I have an air impact wrench. It has several torque settings. I start with the lightest, hold the Flywheel with one hand and tighten it with the impact. If that doesn't seem tight enough I move the setting up one, hit it again.
At some point it will be about right.
If I want an exact torque then I put the bike in gear, Hold the brake with one foot then use a torque wrench. If I can't hold the brake that way I can use a 2x4 cut off in a wedge shape, push the rear brake pedal down and either jam it down with the wedge.
The same procedure works for the front sprocket too.
Leo