Well, the sides of the neck, which were giving me trouble in the BBS department. I realized that my beard growth is symmetrical around my jawline, and since I was going toward the ear at all points, I should go across from the bottom of the neck for the second pass, as I was going across from the sideburns above the jawline.
What a difference! All but right under my chin is as smooth as my cheeks now. Just thought I'd share to give fellow n00bs some hope. I can now do 3 passes no problem. Remember, if you're not getting smooth, look to the first and second passes and think about direction.