409 worked in with a tooth brush does pretty well on oily residue. Hobie also sells a boat cleaner that works well. They are formulated differently but seem to be about equally effective in removing my local crud. Here's a before and after in the Drivewell area:
As you can see, my boat is white so deposits show up easily. The Hobie brand is probably more environmentally friendly. For the toughest stuff (rubber skid marks etc) or a good deep cleaning, I use a cleaner-wax (like Maguire's) -- but only on the smooth (bottom) surfaces.
When the hull is clean, I like an occasional application with Hobie Protectant. It puts a nice shine on the boat and holds up a little better than 303 on a side-by-side test. Here's what it looks like on my 3 year old Adventure:
I spray it on and chase it with a damp rag right away -- quick and easy to use. It's quite slippery so watch where you use it.
