Hoogie, I'm not sure of the exact torque setting to tighten cranks, but limit of strength with an 8 inch spanner is about right for conventional cranks. I use a thin smear of grease. Afterwards, I tighten after every ride, not to the original torque but about half the amount. I need to do this less and less.
I'm not sure if it's the same for splined cranks. Hope this is of some help.