definitely lay off the speed burst until you see an opening. You have to be really patient and follow your blockers, especially the fullback if you are using one.
With the speed burst, don't tap it, hold it down. If you tap it, you aren't going to outrun anyone.
Also, don't limit yourself to a specific set of sliders. Everyone is a little different. Bump up the run blocking if you have played game after game and still can't get a decent running game going. I used to limit myself to slider "sets" you see on here, but once I started using whatever I was most comfortable with, I started enjoying the game a lot more.