The subject of "how do I sell my timeshare?" has been addressed again and again and again in these forums; answers are already sitting around and readily available from many past posts. Just conduct a search of these forums and you will easily find LOTS of posts providing good, clear, specific advice and detailed recommendations on how to proceed. If you still owe money on the timeshare, however, don't even bother advertising until you have attained free and clear ownership --- NO ONE is going to buy into someone else's exisiting debt when there is so much available in the resale market owned and offered "free and clear".
There is no "easy button", but it's not difficult either. Like it or not, YOU have to spend the time and expend the effort to sell your timeshare yourself, by pricing it competitively with (or below) all others like it and by advertising on one or more of the numerous free or low cost timeshare sites like RedWeek, Bidshares, MyResortNetwork. There's also eBay. Craigslist is free. A closing company (generally paid for by the buyer) will handle any and all other details such as deed preparation and recording and escrow and disbursement of all funds. Your mission (and it's truly yours and yours alone) is to first FIND a buyer, by the methods described above and as described in detail in countless other posts right here in these RedWeek forums. But no matter what you do, NEVER pay ANY company an "upfront fee" under any circumstances --- you can always and easily buy better, cheaper, more effective advertising entirely on your own without ever even speaking to ANY useless and parasitic so called "marketing" company, charging upfront fees to do absolutely nothing of any real use or value. Good luck.
KC