I also have a couple of domain names, but selling them "directly" is not quite easy. I too want the "secret" for directly selling or simply selling a little "faster".
Well I've sold around 10 domains in my life. Never made a killing, but had a couple of good hits. And auctions have all been complete failures for me. Direct selling has worked. (I don't want to say "worked well" because it's a slog). But finding prospective buyers and reaching out to them via email / social media has been decently successful. The thing is, you better have a good domain if you're going to bug someone. (If it's not worth over $1000 at auction, you're not going to get anywhere IMHO).
I have no idea how to sell a domain worth less than $1000 for that reason. I guess you just put it up for auction and pray.
My biggest success was a direct sale of a name that was the exact name of the company that bought it. (But not a trademark). That took about 2 days to sell. If only they could all be that easy.