They can be terrifying... But it's really not so bad at all. You just have to remember two things; hold it at about 30º to your skin and apply no pressure (as none is needed). You'll want to make two to three passes over your face and neck (with a quick rinse and re-later in between). The idea is to "reduce" your beard with each pass rather than try to get it all at once. Cartridges have up to five blades; with each stroke the passes go up exponentially (5, 10, 15, etc.) while a DE is a single blade; one blade and three strokes is still - three passes. You already know how to shave in general and with these it's really no different aside from the above.
Throw out those ridiculously expensive cartridge razors. Doubled-edged razor blades are 1/10th the price. And that canned goop is not good for your skin - it's full of chemicals. Real shaving soaps and creams produce much better lather, are generally all natural and work very well.
Almost guaranteed you'll have a closer and more comfortable shave! I never liked shaving, and shaving every day was absolutely out of the question. These days I love it, even look forward to it - every day (except weekends, heh).
There are a lot of HOWTO videos on Youtube if you're curious about the technique(s). Check out Mantic59
's videos especially. As for vendor, I've been more than happy with West Coast Shaving
(thought they're here in the states).