I actually use a large bolt that has been fluted and tapered using an angle grinder for my puller. The bolt doesn't have to be hardened or anything special, the job it is doing lets you use pretty much any bolt that is just larger than the sludge trap tube size. The taper you grind it to lets it start to fit inside the tube then as you wind it down harder and harder it grabs the sludge trap and starts to spin it. Once it starts spinning you just keep turning it as you apply upwards pressure on the spanner/socket.
I will take a photo of the bolt and share soon.