Is it even possible to find such domains on expireddomains.net? Or do all domains with traffic go either through a preliminary auction or are already being sold by resellers?
Yea it is possible but slim chance of making sales because mostly people abandon domains because they stopped generating traffic. If it was working for them they would not let them expire. I made few money from expired domains and typos. Not something that I am proud of. I might have paid hosting with it or something.
When looking at expired domains that "generate traffic" you need to be incredibly careful and do your own research. Many of these pages deceive you and the for example GoDaddy appraisal tool algorithm to make the page look more valuable than what it actually is.