Sockjunky. LOL. I’ve never used wooly nylon on a serger, but yes, it comes on cones that would fit on a serger. It’s super thin, so it doesn’t affect your gauge, but it adds a lot of strength. After I did the toes with the wooly nylon, I wanted to reinforce just the soles but still keep knitting in the round. So I carry a strand of nylon across just the soles and simply snip it at the end of each row. When I’m all done with the socks, I’ll turn them inside out and snip the nylon ends pretty close to the fabric. Since the nylon will be knitted all the way across the row, it should stay in place. The operative word being “should.” So far, the reinforced parts of these socks feel very sturdy but still soft and flexible. I tend to knit my socks bullet-proof.
So what are you knitting instead of socks? BTW, I’ve already got my next pair of socks picked out: a pair of tabi socks out of silk. Silk is very strong, so I might not have to reinforce them. I have to read more about the properties of silk.