The don't need to work with a broker like TSS, but would need a closing agent. They would still need to have a signed written offer and present that to Disney for their Right of First Refusal (ROFR).
You can handle it yourself, you could use a closing agent but you don't have to. The process is the following.
Contact DVC and get their transfer packet.
Fill out the transfer letter and submit it to DVC member admin along with a copy of the contract that spells out the details.
DVC can take it at that point but if they don't, they'll give a ROFR waiver.
Record that waiver and the new deed and fill out the new tax form that OC how has.
Fill out the second transfer paper that comes from DVC with the waiver and send that and a copy of the recorded deed.
Minimum cost about $40 for the recording fees. There are discount companies that will do the closing for less than the full service companies. The big risk is that Disney may take it if it's a good price. It's also illegal to put a price that's different than the actual sale price.