There is, often times, a bit of a pause between collecting waste vegetable oil from the various sources that you may have. I only make Biodiesel for myself, so I frequently find that both of my trucks have full tanks and that my single 55-gallon storage drum is almost filled with Biodiesel. Now is a good time to clean-up the garage and make some room to move. One thing that I decided to do was empty a few buckets and cubies of some real bad left over oil that was mostly water and settled solids. Though the good WVO was slim, there was too much to throw away. So I poured the stuff into the main reactor of my possessor and let it cook overnight. The next day I was able to drain off about a cube (4.5 Gallons) and salvaged about 10 gallons of decent WVO from the left-over dregs. At first I was worried that the drain would become clogged, but all of the yucky stuff drained out without a hitch. Now I’ve got almost half the oil I need to start a new batch. Amazing what a little creativeness can do.

I did the same recently with some dodgy curry house oil.-I collected ~80lts of stinking/slimy fluorescent oil/water mix(been stored outside in the rain)-Thought I was wasting my time-anyway screened it through a gauze into the processor(the smell was awful-there were cigarette butts in there and god knows what else).Heated to 50c and chucked in 20 lts of glyc byproduct-immediately turned to whiteish/yellow mayonaise.(Now I knew I was wasting my time!)
Decided to try adding a further 20 Lts of glyc product-this time the oil went a more normal browny/clear-anyway pumped and heated for a couple of hours and let it settle for a couple of hours.
Drained off about 50 Lts of very thin watery glycerin,but the oil behind the glycerin was a beautiful normal golden yellow-it only yielded 50 Lts of oil but its 50 Lts more than I had and about half towards the next batch.(I only use glycerin to de-water my oil,but never tried it on such wet oil-but it seems to work)
As you say,it just shows what can be achieved if you add a little thought