If you use a fast shutter speed, the 'X' speed of 1/180th of a second and a small aperture to get DOF, then you have virtually 'killed' the ambient, if you take a picture at those settings without flash it would be just a black frame.
Then your effective shutter speed is the duration of the flash which will be at least 1/1000th of a second, much faster than that if the flash power is turned down, around the 1/5000th of a second mark at half power.
This means that obviously hand holding becomes possible. As the flash to subject distance doesn't alter much as it's set by the focus manual everything becomes possible. My 'bug hunting kit' consists of my K10D a set of bellows, an old Takumar 135mm and an off camera manual flash set on 1/16th power. Focusing is by moving the whole camera/bellows/lens/flash contraption backwards and forwards.
As the only things to think about is the framing and focus it's very quick to use, the 135mm lens puts me further away from the subject, out of the insects 'radar' range.
http://www.flickr.com/photos/chris-judge/4050045816/
Any shake reduction is obviously not necessary.
Chris