..Is there a trick to getting the manifold gaskets to seal well? Do I have to torque the manifold bolts in some order?...
Biggest "trick" is ensuring they are as flat as possible.
The surface between exhaust and intake manifolds needs to also be flat, clean, and a good gasket.
With the two manifolds lightly bolted together with gasket, now temporally bolt them to the head with no gasket, again snug but not really tight.
Now torque the bolts holding the intake to the exhaust.
Remove manifold assembly from head.
Take assembly to machine shop to have them surfaced (flattened) together at the same time.
Reinstall assembly with new gasket.
Snug all bolts and torque from the inside working out.
Grigg