Ditto on model #. That's another way to attract serious buyers. I'm still a year out from purchasing but I'm searching first by model # because I know what I want as first choice. I look at ads for preferred models regardless of price. I only look at ads for nonpreferred models if the price is super attractive where it's worth me giving up the floorplan/manufacturer that I prefer.
Here are the four P's of marketing (or at least were 25 years ago when I was in school!) with oversimplified definition. If you goon up any one of the four P's, you increase the difficulty in selling.
Product: Is the product good?
Place: Am I selling it in the right venue(s). I would argue for you this means nationwide websites instead of local craigslist.63
Price: Is is priced appropriately?
Promotion: Am I casting a wide net in promotion and the quality of promotion high?
Hope all of this is helpful to you. Sorry it didn't work out.