However, I strongly urge you to learn both methods as you develop. You may or may not be able to hear the difference. These are more advanced techniques you will want to develop later. This will produce a clean, single note. Not the prescribed method, but it proves that it can be done.
Some players do tilt their harp upward.
If I may borrow a tip from a recent seminar by harmonica virtuoso Stan Harper. Stan strongly urges us to learn our instrument. The tone, vibrato and all the other neat stuff will come later. All these techniques are worthless if we cant play the instrument. The best way to learn our instrument is to learn to read music then practice scales and drills.