It's quite easy, and no, you do not need a closing company.
Advertise your unit on TUG, Redweek, and other sites (if you need suggestions come back here).
Once you have a buyer and your money, you just sign your membership papers and send them down to ISCO, attn: membership, along with the info of who the buyer is. They charge ~$135 for the title transfer. You or the buyer pays ISCO the fee.
They will also work with you to hold the membership papers until you let them know that the funds have successfully transferred:
- The buyer sends you a deposit,
- you sign the papers and send them to ISCO asking ISCO to hold them until you give them the ok to re-title the unit,
- the buyer checks with ISCO to confirm that ISCO has the signed papers,
- buyer sends you the rest of the money,
- you wait for it to clear, you let ISCO know,
- ISCO retitles the unit.
They are quite easy to deal with.