Selling quickly with domaining is never a good idea. If you try to liquidate your domains you will usually end up with reseller prices or lower. The best strategy is to price your domains with Buy Now price on Afternic and Sedo and wait for an end user.
If no end users are searching for your domain then your domain is not good. Outbound rarely yields good results unless it is an exact match. Even still, you have to wonder why the end user never typed your domain in?
If you have many low-quality domains, then you might consider dropping them. The yearly renewals will cut into your profits and it is better to own few high quality domains.
1 domain worth $10,000 only costs $10 per year to keep.
100 domains worth $1000 each costs $1000 per year to keep.
Many domainers only get 1% sales in their portfolio per year. If you have 100 domains and sell 1 for a $1000 every year, then you will pay all of that profit to renewing the other 99 domains.
Invest in a few high quality domains where there's no question their value. Put a retail buy now price on Afternic and Sedo, renew for a few years and forget about it. That's the best way.
Hope this helps.