I like instant sale offered by Epik and Namesilo. Maybe a few others like Dynadot, Uniregistry, Godaddy, Namecheap may be offering the same thing.
For reaching Chinese buyers I think Afternic is a good choce, because strangely Chinese people don't seem to buy domains if not offered by Godaddy. I dropped 30 3 letter .co's just because Chinese people insist on Godaddy. But I tested my domains listed on AN at Godaddy, and they were not visible.
Sedo is good for reaching European buyers, but it was better. Now they have many mistakes. It looks like their agenda is not selling domains owned by domainers. They use those domains to get traffic, and then do what they want to do with that traffic. They don't fix those mistakes, although they are obvious.
Efty: considering using it for good landing pages, and IP checking. Still thinking.
Use your own server?: But domain need to be transferred in a way acceptable to the buyer. They don't want to get scammed, by paying and getting nothing.
Outbounding? : Same as above, you can find a buyer, but then you need to sell somewhere.
.........
Outbounding is a must, otherwise sales don't recover renewals. But outbounding doesn't work either. Maybe when it is mixed with good landing page, it may work. You can sell 10 domains and recover registration costs of 1000 domains, but what to do with all 990 domains which have the same quality as the 10 sold ones. Sitting on them costs more than registering them. It is a big dilemma.