So...you took whoever Dr. Bob picked, and now are waiting to see what happens with the lines. No matter what happens, you are going to take the other side, but are waiting to see how far they move...
Correct?
I can't speak for everyone, but I usually bet a few teams I like early in the week if I feel that line movement on that particular game is likely to work against me. Unpopular favorites, for example, or a popular covering-machine of a underdog (like Navy). I only make these bets if I like my chances of winning no matter what, but if Dr. Bob can make the line keep moving in the direction I thought it would, and if it crosses a key number, the option of shooting for a low-risk/high-reward middle is a nice bonus.
There was a good example of this last week with the Kent State/Ball State game. Early in the week Ball State was available at -17. I liked the line at that number and figured that with their strong quarterback and playing at home it was likely to rise, so I grabbed it. I can't recall if Ball was a Dr Bob pick or not (I think it was, but I'm unsure) but the line did rise like I figured it would. On Saturday morning it was briefly at 21.5. Once it became more than a three-touchdown game I played the opposite side.
When the game ended with the Ballers winning by 21 I was a very happy guy and thanked the touts for giving me that middle.
BUT, I would say the most important thing is you must like the original bet you make as a standalone play. Wagering with only the intention of middling can't be counted on.