Well I also had problems with the foam handle cover sliding around on me, I eventually ended up pulling it off and gluing it back on with some *Goop. The trick is to pull the foam handle off and put a bunch of the GOOP inside the foam, then slide it back on, twisting it as you go. This gives a nice uniform glue coating that secures the entire handle and avoids any lumps.
As to technique, note that I'm mostly left handed, and left eye dominant, so you may want to swap sides...
At the beginning of a swing, I hold the MM almost vertically in front of me, with my left hand loosely guiding the handle just under the head, and my right hand firmly gripping the end of the handle. I "throw" the head straight up with my left hand, while pushing the handle up along the same line with my right. As my left hand reaches almost full extension, I let it slide down the handle onto the foam grip to just above my right hand (the heel of my left hand is touching my right thumb) as I continue to push up with my right hand. The idea is that the maul head ends up almost vertically above, but slightly ahead of your shoulders, with your arms almost straight (but not locked) and both hands at the end of the handle next to each other.
As you reach this point, without pausing, you start swinging your arms forward and down, keeping the handle as a straight extension of them. Primarily your arms should be guiding the fall of the maul head, but any acceleration you can give it at this point will help. Throughout the entire swing, you should be focussing your eyes on the "target point" of the log you are trying to hit.
I reccomend you wear gloves for this, but you want ones that are snug fitting, padded palms are helpful, though not essential (a snug fit is more important) and they need to be a material that is conducive to sliding, not "grabby" - (i.e. leather is preferable to rubber) and wear resistant. I just picked up a pair of gloves at the local True-Value that have a goat skin leather palm and fingers, with a spandex back. (about $12) So far they seem ideal, wil need to see how they wear. (I don't use those "one size fits most" cheap generic leather work gloves, I find the way they fit so loosely, they slide around and irritate my hand worse than the stuff I'm trying to protect it from.)
Gooserider