T&T: bilge cleaner?

[David H Sorenson]

The mechanic just winterized the boat and changed oil today.
Unfortunately, he left an oily scum in the bottom of the bilge. I know
this has been discussed in the past, but what is a simple, "green" way to
clean the crud out? The boat is on the hard now, but when it goes back in
the water in the spring, the bilge pump no doubt will discharge and out
will go what is there. What is is a good "product" or substance to
emulsify the scum so we can deal with it?

DHS
Duluth