Rick

I've cleaned a lot of hulls in my time but I don't think I ever ran
across a combo of mud, oil and deisel fuel....whew! At least you have
the boat out of the water. Heck, after Katrina and Rita at least you
have a Boat! A lot of what you can do will depend on what the yard will
let you use for environmental reasons. Before spending too much on
some fancy fiberglass cleaners I'd try a good mixture of good old
dishwash soap and water which is generally pretty good for dirt,
grease and oil. good sponges and . a lot of elbow grease. still not
working? Just smearing things around?. West Marine has some really good
Fiberglass cleaners which while not cheap have always done the trick
for me. There is one which is made for non skid decks, It seems to be a
little more "intense" that regular FG cleaners but it really works
well on smooth FG as well. Takes off those inconsiderate black rubber
footwear marks that no amount of soap and scrubbing will seem to
remove. Use sparingly.
While the boat is on the hard don't forget to check for blisters and
fix any if you find them. This might also be a good chance to slap
another coat of bottom paint on.

Cap'n Phil