The white SpeedPaint is actually a runny light grey that shades the panels of the stormtrooper armor. If you're not sure how well a paint job will work just try it out. If you're really worried practice on some cheap toys or something and just study how the paint affects them.

Slap chop works best with models with lots of detail to catch the dry brush, but works fine on just about anything.

If you're going SpeedPaint washes aren't necessary, they're essentially a base coat and wash in one step. I would recommend some normal paints to do highlights with. Highlights are pretty tricky with speed paints.