During dog rounds, go to the window facing towards the fly trap and have your partner lay on the floor on the left side of the window (facing the that one door that leads toward the trench gun).

After he does this, run from a distance andjump then in mid air hold B. You should then be on top of your partner viewing exactly what he sees.

The dogs then should run until theey're right in front of. Stop, then run in place giving you the freedom to take your time aiming and shoot.