I have to apply regularly for business visas for African countries and they are a pain in the neck, generally requiring letters of invitation from you local contact, often endorsed by the local Police, along with company letters, copies of household bills, bank accounts and all kinds of other stuff. This is usually a tit-for-tat thing because Britain makes it so difficult for other nationals to get UK visas. The worst visa to apply for is Nigerian, which requires the use of a web form that's so crap and designed to frustrate that I just hand it to a visa agent in London who does them all the time. Others like Ivory Coast require you to travel to London where you enter a stinking filthy consular office, a delightful little piece of Africa in Belgravia, to be fingerprinted for an e-visa. Last time I went down they couldn't get my fingerprints because my fingers are smooth from lots of DIY so after three hours they gave up and hand-wrote an old style visa. Oh and the fees aren't modest; that for Nigeria costs $475.