I have gotten braver with the mechanical yard sale onees. Actually, I have gotten to trusting DH more to clean and oiil them!
The other ones, just oil thoroughly and try to keepp the lint cleaned out.
By the way, some of the much older machines have sort of a wick like thing by the bobbin area that looks like it should be picked oout. Don' t.
Maybe some of the people that really know about these machines can tell us more about it