Your suggestion is the way that it's done. Some inspectors might want you to use a water line just to be clear that it's mechanical protection and not a raceway. Be aware that your duct might change the classification of the area that it enters, unless it's sealed. Even if you do seal the duct, it doesn't need to be chico. Table 8 is for tubing fill for multi-conductor cables, unless the raceway is short.
