I put my dirty chains in a glass bottle (Ball canning bottles work really good) and pour in some WD40 (Sometimes I also use mineral spirits, in place of the WD40 or a combination of both, but have been using WD40 more and more as the news about chain side plate embitterment cause by some types of mineral spirits had worried me.) I then cover the bottle and shake/agitate it and then let it sit a while then I repeat the agitation and refresh the WD40. Then I remove it from the bottle and put it in a small, shallow aluminum foil pan that I save from frozen food stuff from the grocery. I spray the chain liberally with more WD40, blasting it with the spray between the plates and rollers till there is enough in the small aluminum pan that the chain is half submerged in it, then I hit the chain with an old toothbrush to get the most stubborn gunk off between the plates. drain the pan. I also use a steel or copper bristled small brush on it if there is some corrosion on the plates that need to be removed, wash the chain with warm water and soap and then blast it again with WD40 to get any left over loosened gunk and dirt off and to displace the wash water then give it a final wipe-down with some paper towels and hit it with some lube like Phil Wood Tenacious oil, or what I have handy at the time, before re-installing on a bike. If your chain is not too rusty and too worn out to start with, the thorough cleaning method might sound like over the top for some I described could get it close to looking and working like brand new again.