What short term rental platforms/sites have worked well for you that I should consider posting the property on?

Still nothing really to show for the money spent so I reached back out to seomeetsrei for guidance and they suggested signing up on more social platforms and another 10K or so in backlink work...

A lot of us here on this platform are willing to help any way we can. 

It is a good platform and I enjoy it, but I spend more time than I should on it.

Bigger Pocket is a very good platform to find people to help you. if you have half a million lying around, then I would say spend some money for these courses. 

What platforms do you folks recommend for listing a Single Family home in CA for long term rental? 

Reach out to Airbnb, they have a platform for that and we used them and they find local photographers that do great work.

I'd probably try FB marketplace first and see how it goes, then if that doesn't help look for a good advertising platform like buildium (which is probably too robust of a tool for what you need right now, but something with just that advertising feature).  

Airbnb/VRBO do bring in about 60% of our bookings but that does leave another 40% to direct bookings and a combination of our other platforms (Marriott Homes and Villas, Booking.com, JetBlue and Allegiant Airlines, Google Vacation Rentals, and more). 

We ran the numbers, analyzed the property multiple times, and based on AirDna, and other platforms, it looks quite promising.