Order in which OR order to

Which is correct?

Do you say “an order to + ing or « order in which to »

Is there an order (to floss in/to flossing)? Do you start with you front teeth or back teeth?

How do you correctly ask the question? Is it correct to have « in » at the end?

What order do you floss, brush and mouthwash (in)?

Do you gargle, swish or swill mouthwash (around in your mouth)

Is the sentence grammatically correct and okay to use in an article?

1 The burning sensation after gargling /swishing mouthwash has me sold on the fact that it does your oral hygiene/health lots of good.

thank you very much