How do you clean SNS pipettes?

Dan Kegel writes:

We've been happily using an SNS in the months since
our bundle o' joy arrived. We use the thin pipettes...
that DS wasn't getting much formula.

Personally, I hated the SNS and couldn't get the tube in my daughter's
mouth. But one thing I remember is that our LC told us not to try feeding
formula through the thin tubes. She said the thin tubes were only
appropriate for breastmilk. The other thing we were told is that you
should try to control the flow of milk by raising or lowering the bottle.
If you're having to change tube size to control the milk flow, maybe that
means you're putting the bottle too high above the baby's head and have to
lower it, somehow.