You have to make sure that the piston is at TDC on the compression stroke so the valves are closed.

Just go a little past TDC so the piston is heading downward again, then feed in the rope, and reverse your rotation.
It works for both loosening and tightening, but you have to think about the direction of engine rotation and where the piston is before you feed in the rope.
It doesn't take much rope. Both valves are closed for several degrees before and after TDC/compression.

I just used this method on a Honda (which run backwards) and it worked very well.