A productive evening
My Adler Contessa de Luxe now works! It has a lovely font. I cleaned it, changed (respooled) the ribbon, and made a few little adjustments. It still has two problems: one of the sticky keys is still sticky (the others aren't anymore), and the bell doesn't work most of the time. But I'm happy, it's the first machine I actually repaired.
I use the same oil I use for sewing machines, it is very thin, low viscosity. I apply it using syringe with the bevelled tip of the hypodermic needle cut off.
I put oil everywhere there's metal moving against metal, it doesn't need much, just a thin coat. Too much oil can collect more dust or even drip inside the case.
I don't know, at least not yet. I've only been doing this for two years, maybe they didn't have time to gunk up.
I use the oil I buy to lubricate sewing machines. Not only I oil everything that is metal against metal, I rub some of it on every spot it I consider it needs protection from rust.
I stopped worrying about too much oil when I read on a typewriter repair course from I don't know what decade that after drying in an oven to put it in an oil bath to lubricate and protect metal surfaces. I won't go to those extremes but made me realise that if I put too much oil worst thing it could happen is that the typewriter will need a new cleaning next year.