I have made a couple 2 ply B-50 strings. When I go to serve them, you can tell that it is made of two bundles. I can't get them to look like a rope, rather I get this funny looking think that looks like two shoe laces wound around each other.

I was wondering, how do you get the two bundles to form a nice rope?

after you form the first loop, you MUST put back twist into the two bundles before continuing with the second loop.  doing the twist dvd will show you everything you need to know about making fl. twist strings!

cjc said it,  I seem to think that it also helps to burnish the string with a piece of leather,  really good hard strokes) while you are doing the final twisting.  Seems to make the different strings meld together.