You need a good power stance, anything where you're rooted to the ground 100% of the weight on the balls of your feet. Quick flips and slaps are required, so weight on your palms is out.
As for nudging, here's the only information you need:
1) You move the table under the ball. So if you need the ball to move left you have to nudge the machine right (UNDER the ball... it rolls).
2) The biggest mistake is the belief that your goal is to nudge the ball to go down your inlane, instead of your outlane. While this can be the case, it's almost never your goal. If the ball is headed towards the in/out lanes your goal is to nudge "up". Both palms should give a good pop to the lock bar straight forward right as the ball is about to touch the centre post between the lanes. The goal is to bounce the ball straight up. Almost every machine has an angled bumper above the outlanes, if you nudge well it will hit this and return to the centre of the playfield. Your goal is to get the ball out of the lanes entirely.
3) Sometimes you'll need to nudge during the game, for example to kick the ball off a wall to stop it from feeding to the slings.
4) Nudging hard enough to trip the pops can keep your ball in the jets longer.
5) The goal is not to really move the machine (well it can be, but not typically), you're simply adding kinetic energy to increase the degree of bounce you're getting off posts, etc. So you don't want to grab and shove, it's really just a "pop".
6) Beware "popping" your palm into the corner of the lockbar. Serious bruising can result.
That's all the gunching advice I have for now.