I used a torque adapter like this:
NAPA AUTO PARTS
You attach it to your torque wrench at a 90 degree angle so it doesn't affect the amount of torque measured/applied. I'll admit that I needed a helper in order to hold the crank, rod, torque wrench, and stretch gauge all at the same time.
I actually found that the old school beam type wrench made the most sense for this, so I didn't have to continually change the setting on my click type torque wrench. You probably can't do this with one of the ratcheting torque wrenches, since it needs to stay perpendicular.