I post regularly in discussion groups on Linkedin. I have found many serious cash buyers there. I just post catchy headlines that attract interest and put my contact info. Many people contact me:). A couple samples -
How My Partner Retired Himself with $50k SFHs in TX - No Repairs Ever
How to Make 17% Cap Rates on SFHs with No Repairs Needed
You would be surprised how well this works :).