The key to doing private (direct) exchanges is to have a resort that is extremely desirable. If you have such a resort, you stand a good chance of finiding people who have resorts in places you want to visit who are willing to trade with you.
If you're week is not a top drawer week, it's a lot harder to find people who want to trade. For those weeks, you really need to work through an exchange company.
For example, I receive probably about 20 inquiries per year from people wanting to do a direct exchange for our Kaua`i week. (Most of them are offering weeks that are not too attractive.) I've had our Winners Circle week listed as available for direct exchange for just as long, and I've never received an inquiry about direct exchange. But, depositing our Winners Circle Week with an exchange company, we've been able to obtain very fine exchanges - higher quality than what is in most of the offers we get for our Kaua`i week.