OnlyWire allows you to grab your homepage public RSS feed, input it, then away it goes, automatically updating the main players every hour.
After playing around with the free service, I know from my analytics that other social networks provide me significant traffic, so I upgraded to their pro package for $60 a year which allows 1000 posts a month and more importantly many more social networks (testing). Set and forget, automatic. No more issues in getting all the latest content onto all the major social sites. If you have two or three forums, then the pro package makes it easy for you to send all sites onto your feeds at once. You can buy as most posts to be posted as you need. Just cost you more.
This has been a bug in my backside for years now, finding a single solution that can do the job properly. I did a search here and nobody had mentioned this one before, and I'd certainly never heard it either, until playing around with affiliate links and discovering them myself.
They've also got an enterprise plan for those who want to submit significant feeds. The single homepage feed has all forums in the one feed, public that is, so you can do it singularly without issue. The enterprise plan, IF you want far greater control, is around the $80 a month range and 5000 submissions. You have unlimited feeds with the enterprise plan. You can upgrade all plans submission level to cater your forum post count.
This can seriously boost start-ups in the right direction, getting all your forum content onto major social networks freely / cheaply, depending on your budget, with a set and forget solution, let alone established sites driving far more social network traffic.
I know I've been struggling to find a solution this good for years... and now I have, I'm not sure whether others are aware of it.