Thanks for all the great pictures in this thread.
Folks running Chinese tractors have major cleanup to do on their fluid spaces, and most opt for kerosene. It is thought to have slightly higher volatiles than the diesel, but I doubt it matters much. We generally drain and then refill with kerosene, and operate the unit with no load for a few minutes, and put it through it's paces...drain, and depending on what we see, do it again with filtered kerosene or new. It is important to remember that kerosene is not a great lubricant, so you don't want to do just a whole lot with kerosene in the unit.
In YOUR case, I'd forgo the running, since you seem to have direct access. I have a solvent vat with a little pump. I'd be tempted to pull the legs off mine and put it under the tractor's drain hole, and extend my hose length, and go to town on it.