Really boobsy all it amounts to is this,
1. Lay down flat on the bench.
2. Lift your feet up off the ground and "kick" you feet back toward your head so that you are on your toes.
3. Grab the bar and lift yourself off the bench. While doing this "tightly" arch your lower back while at the same time pulling your shoulder blades together. Then let yourself fall back onto the bench.
4. You need to be tight from your calves to your shoulders and elbows.
Its easier to do this with some weight on the bar as opposed to just using the bar (for me at least).
Just practice it. You could make this part of your warm up even if you dont feel comfy using it to do the actual lift.
If you do it right its not a comfortable position. But its rock solid!