Nathan-
Are you referring to: Runners at first and second, first baseman playing behind the runner, and first baseman sneaks back to first base for pickoff from the pitcher?
If yes:
1. It's a rare play. Do you really need it in your playbook?
2. But if you want to run this play, have your pitcher step behind the rubber on the pick so that if the timing is bad, he can abort the throw without balking.