Honestly, I wouldn't worry about lowering the bar in 3 or 2 seconds or whatever King is prescribing. Waterbury, and other top trainers recommend simply lowering the bar in a controlled manner without worrying about how long it takes because the whole tempo thing isn't backed up with any scientific evidence. During the beginning phase of the BOM I followed the prescribed tempos, but during the intermediate program I didn't worry about it at all and still had some nice gains. As far as having a spotter is concerned, you've just got to lift a weight you know you can kick out the prescribed amount of reps with, and just be careful about busting out "one last rep", if there is any doubt that you might not be able to do one more, just rack it.
Also, here's a little article by Waterbury, stating why you should lift as fast as possible
Lift Fast, Get Big