Can the underwear be steeped in the softener?

Softener is designed to be used as a post-treatment. It is not a good idea to allow washing to stand (be steeped) in the solution. Many people are sensitive to the ingredients in softeners and, if you are one of those, you should avoid the use of softeners. As a general rule it is best to avoid them, anyway.

I don't steep my underwear in softener, however, one I have washed them I do rinse them out in fabric softener. I dry my clothes on a clothes line not in a dryer. When I use fabric softener in a final rinse they smell fresh and clean and are much softer.