...currently working on a 1936 Columbia with years (decades) of caked on, very thick, hardened grease/oil.

Finding the master link is the hardest job, but when removed from the bike, I place the chain in a plastic container, spray both sides with easyoff oven cleaner, let it sit for about 5 minutes, then use a parts cleaning brush to loosen the real heavy stuff, then wash with water. Wear gloves and work outside Might want to weat protective glasses in case of splashes.

Next step is to spray with wd40 (water displacement), hang chain and lube it. . Whole process takes about 10 minutes. Takes the chain down to bare metal so you can determine if is rusty or just dirty. (rusty gets replaced)

Not recommended for bikes you are currently riding or that have received normal mantainence, but if you have a much neglected CV ride, it works well. I gong to look at a 1954 bike this afternoon and it will most likely need this treatment

This method is way over the top for most cleanings, but I thought it my be useful for others like me. Also should mention that it will remove paint, anodixing, etc., so do this only if the chain is off the bike.