The dishwasher! I would have been afraid of getting gritty soil into it. But I guess small tools wouldn't carry all that much grit with them. (I've been paranoid since an attempt to bottom-water some trays in my bathtub contributed to a clogged pipe.)
I keep handy a barbeque grill scraper/steel brush for scraping and brushing shovels and hoes. If there is a puddle, I'll swish the shovel in that to get it pretty clean. Or use a hose and sprayer on "mist".
My theory is that clay and dirt hold water next to the steel and encourage rust more than plain water would. The water runs off or evaporates quickly, but I think that clay holds water longer.
Besides oil on steel parts, I use mineral oil and parafin and beeswax on wooden handles.
In theory you can coat metal with a thin layer of wax by using Johnson's Wax or parafin dissolved in mineral spirits, but I think that would scrape right off a shovel or hoe. Nice for winter storage, thoguh!
