I have the differential out(W124 1995 E220), I am planning to flush and clean the diff removing rear cover. Also planning to remove two flanges to clean some rust.

1) Is there anything that I should be careful about?
2) What are the minimum parts I need.
3) What is the best fluid to flush the differential? Can I use diesel?
4) Manual mentions Loctite 5900 for newer non-machined diff cover and Hylomar for older machined cover as sealant. I have Loctite 5900 already and I think mine is machined cover, can Loctite 5900 be used in place of Hylomar?
5) How much time should I wait after applying the sealent to fixing it, Can I fill oil imidiately after fixing rear cover?

Thank you