Hi booblet - re the technical aspect of your question. I'm not sure what you mean by reply individually? If you mean write a separate reply to each of their posts on your thread, you can do this by clicking on "quote" or "insert quote" in blue in the top right of their post, and then their post will appear in the new window. Then you can reply to that person, though everyone will see the reply.
If you want to reply privately then you just send a pm to each person, and if you want to quote their post then do what I suggested above, and then copy and paste all of that into the pm (including the formatting codes), and it should appear (and then discard the reply where you started the quote on the thread).
Hope this helps!
Hurdity x