Advance specific local knowledge and/or experience is always the best. Assuming that the travel is as an employee of a company that has a contract to perform services in these locations, it seems reasonable to assume other employees have been there before you, and have this critical knowledge. If you do not know them, seek them out, perhaps even consult your supervisor or corporate security officer(s), or even people who are your "customer" who have this knowledge. They almost surely will be able to give you advice based on actual local knowledge and experience.

Sorry if this a "no-brainer" that you are already doing, but I've seen a co-worker go off on an international trip, arrive at the foreign airport without having a Visa. If he had bothered to ask anyone in the company, he would have been told he needed one, and how to get it, as many of our employees had made the same trip before him. As he never asked, everyone assumed he knew what he was doing. As you might expect, excitement ensued when we got word he had been arrested.