I do it every time by mail and I travel internationally frequently. Sadly, a lot of people here, yourself included, haven't tried it but rely on Google to give you the right answer!
Often people want advice and more often than not there's several solutions to a specific issue. I wonder why you're in a group which has "Advice" in its name. But you're spot on, those that use visa agents try to justify spending a stack of money on something they could do themselves and always quote the "I've better things to do with my time" and then spend hours on Facebook justifying themselves