I also have problems with hello, and h in general. I often use brief variations of words to help me pronounce it fast. One example of a hard word is as you said, "hello". Although I often get a block on this word I pronounce a silent sch/tch-sound before(in the back of my mouth), almost like breathing. This seems to work for me. Or I just try to focus on the L and say 'ello. Usually does the trick!