Im in the same boat as you... ive been trying to learn the 8 break for the past couple weeks and through it all ive learned a lot of what not to do. As they said if you jack up over the cue you are almost guarenteed to have it come flying off the table to the right side (my gf wont stand anywhere on that end of the table anymore when i break) The other mistake I was making seems to be another common one. I have a fairly strong straight on break... I was using the same speed trying to break the 8... The other mistake I was making is if I mishit the second ball I would scratch almost everytime in the right corner pocket. (I break from the right side)
Ok now for what I have learned works: As they said the break speed is important and I was shocked at how easy I could hit a tight rack and still send the 8 to the side pocket. The other benefit to this in my opinion is if hit correctly it spreads the balls enough to get a fairly good shot at a couple balls but keeps the table bunched up some so it makes for more of a thinking mans game which I prefer against people that can run the table on me if I give them a chance. Also as far as the problem about being too jacked up over the cue... im not comfortable holding the cue down against the rail so I actually take my fist and make an open bridge using my fist and the rail to make the V for the cue. This works for me because im using less speed so the cue doesnt pop out of the V. I also use a little bit of low right to draw the cue into the long rail to help make scratching in the corner less likely.
After a week and a half or two weeks of practicing I can pretty much get the 8 ball moving towards the side pocket 8 out of 10 times. Sometimes it goes in sometimes it hangs and a couple times its gone toward the side pocket, got hit my a ball and went in the left corner instead. I pocketed it twice in a row against someone that said he was going to kick my A$$, he packed up his cue and went home.

Good Luck! btw Id only use it in the league if I was up a game or two because i still scratch from time to time. (league being APA)