What is the correct term for "rubbing statues' parts for luck"?
Solution 1:
I would call it statue burnishing or statue rubbing. Roadside America has an article titled: Statue Burnishing Etiquette.
I don't think you'll find single word for this practice.
Solution 2:
I think superstitious is the correct term for this practice.
In some parts of Asia I'd say it's more religious praxis; or just traditional, if you like.