I wonder if social networking/PR is something that can be learned
Absolutely! I had no real idea about this sort of stuff when I took over the GameDev.net Facebook page, but after a few months of experimentally posting and paying attention to what worked well and what didn't I got the hang of what our audience seemed to respond positively to, and the page is now fairly active and very popular with over three times the number of fans as I started with a more following us every day.
Both Facebook and Twitter provide analytics with quite a bit of detail, so you have solid data to learn from: if a certain type or style of posting drives away fans you'll see it right there in the analytics, and likewise for things that work well.
You can also read up as you have already been doing to benefit from the experience of others and gain some general tips to get you started.