Merchandise that is brought into the country for a limited time and for a specific purpose, knowing that the goods must be returned to their country of origin in the same condition in which they arrived, can be considered for temporary import. The application for temporary importation must list and give a full description of the equipment, specifying the name and ID number of the equipment, including brand, serial number, and value. Any item that is shipped by truck should be listed as part of the detailed inventory. You must leave an access aisle in the truck when loading so that Customs Inspectors can get to everything listed on the inventory manifest.
All equipment, wardrobe, props, etc. going into México and coming back to the U.S., or elsewhere, at the end of principal photography will enter as Temporary Imports. You are not required to pay duty on temporary imports going into México and have one year from the time of import to return these items. You may renew for one additional year; but after that, temporary imports not returned are subject to fines of up to 400% of their declared values. At the end of your stay in México, you must account for each item that came in on a temporary basis.
Everything that will be used up (expendables) must enter the country as a permanent import. It is important not to mix goods to be imported temporarily with those imported on a permanent basis.