Can you do a TWO HANDED FIGURE 8?
Learn to lead with both hand's, then after a day or two of doing this, it will suddenly leap out at you
The 3-beat weave is simply a transition between leading with the left / right hand.
Good luck!
Check Youtube for Meenik's (Nick Woosley from "Playpoi" I think) weave tutorial, he has a couple useful exercises that will help you learn it. Although everyone I have taught it just had to learn what I mentioned above, and they were able to weave in no time.