I have had excellent results with a Marpac fluid extractor. I use the thing to drain oil out of the engine and to keep my bilge bone dry. It simply works.

Defender carries a couple different models. Yeah, it is a bit large... I leave it in my dock box. But the thing just works... I love it.
http://www.defender.com/product3.jsp?path=-1|311|2349109|2349116&id=1345777

I make sure I have cleared it of one fluid before taking on another... try not to mix oil and water... as that is difficult to find a dumping place for. But the unit will suck up the last drop of any liquid from any sump or source. So if you are concerned... I do recommend it.

BTW my Pacific Seacraft Orion backs like crap... I mean it goes backward, but controlling where it goes is really a crap shoot. I know exactly what you are up against. Those long keel boats are just that way... add a bit of prop walk and forget it. Best thing I do is get it moving backwards, then ease off the throttle and then try to steer it... but control is not easy, and any current or wind just screws it up. Leaving the slip... I walk it out and then give a burst of thrust and take advantage of the propwalk to put me in the right direction. Otherwise, I love my boat!