What you're looking for is independence, but also realize that each finger can trigger different pads.
Back when I was a wee lad with a practice pad, my teacher, who also happened to be my father, would get two drum books and put them side by side. I was to copy line 1 from each to a new sheet (to help learn writing music), but have one book with upward flags, the other down, as if a snare and bass line. Then I would have to have one hand play one line, the other hand the other line, and then switch.
What really got complex is when one line was 16th based, the other triplet, or when they were in different time sigs.
The concept soon becomes similar to a keyboard player running a walking bass line. One hand must simply go, and work as a complete entity by itself, regardless of what the other hand does.
In this sample, one hand is playing the kit, the other is all of the percussion besides. http://www.zendrum.com/mp3/ZendrumIndependent1.mp3
Its all just practice.