I do pretty much the same as listed here. I just remove the barrel,and and nipple, and get a metal bucket and fill it with hot soapy water, and do the pumping action, and then run a wire brush down the barrel a few times, and when a clean cloth comes out clean, I fill another bucket with hot clean water, and do the pumping action again, then pour hot water down the barrel, and then let it steam dry, and run a dry patch down the barrel, and then a patch with Rem oil, and wipe the barrel, and other parts lightly with Rem oil. As for WD 40, I don't use it for rust prevention, but maybe they changed the formula, as I have read in their ads long ago, that some of the multiple uses were rubbing it on arthritis areas, and such. It said there was nothing harmful in WD 40, as it was mostly fish oil. Now the cans carry a warning label that sates not to get it on the skin.
Wayne