Not sure if this helps, but...
I'm a very socially awkward person myself, so I found two ways of making cosplay friends that worked well for me. One was that I just posted in the Seeking Cosplayers forum, asking if there were any cosplayers in my area. I just kind of got to know a coupe of people over private chat in my general area, and also on Facebook. I met one of my best friends on here, so although a strange method, it can work for sure
Also, I'm not sure about your specific shyness/anxiety level, but I found with mine, it was easier to get to know a person online before meeting them in real life. Just helped lessen the awkwardness and fear in a way
Also, although I don't see all my online cosplay friends regularly throughout the year, they also go to cons and I can meet up with them there easily. Being quite well acquainted with a person helps make the real life gathering less awkward.
Another thing is maybe seeing if you have friends who might be interested in cosplay. Usually it's the nerdy/geeky friends who'd be totally down with dressing up as characters from their favourite fandoms. Two of my best long-term friends now cosplay (one discovered it on her own, the other I introduced cosplay to her), and it's great
Because I already knew them, it was less of finding a cosplayer to be friends with, and more of a friend to cosplay with. You've already got the trickiest part down.
Both of these are more pre-con friendship making tips...
Hope this helps a little xD