Generic sewing machine oil should be fine, even in the long run. The less additives the better. I guess we just try to find the very best of the old machines, but it's still arguable how much we can improve on a basic good quality oil. Some additives have shown to cause trouble in the long run. I think Singer made a point of using their own oil, but it was a purified, acid free mineral oil, neither to thin or too thick, no additives at all. I think it was the equivalent of SAE10.
I have a beige aluminium 201, the same paint as your 401, it polished up very nicely with autoglym super resin polish (for cars). It's the liquid type that dries to a whitish film, and then buffs of with a cloth. Many brands make a similar.