If you look at the hub, you will notice one side has a bevel on the edge. When you put the hub in the spool, have the bevel facing you and the string coming off the spool counter-cloclwise.....or going OVER the spool to the LEFT. It will always be correct then.
The dubbing is a snap. Just get a couple "strands" caught up in the junction of the thread and the hook-eye, like is done sometimes with the thread and the hook-shank in "normal" tying, and your set to go. We tie some nymphs with wire as thread and it too takes dubbing just fine.
.....lee s.