Here's an idea for the ptu flush.... Without looking at a diagram, what if you removed the fill plug, drain what you can with a suction device, then put a catch basin under it and using some cheap fluid, funnel it down the overflow tube? Again, without seeing a diagram I'm not sure where the overflow tube is, but if it is on the opposite side of the fill plug, you might be able to force enough down the overflow tube to try to pump some more crud out the fill hole.
Just an idea!
