When your opponent opens with a Precision (or any other Strong, Forcing and Artificial) 1, I recommend trying to interfere. Best is to preempt (the higher the better), but if you can't preempt, it is useful to be able to show a 2-suiter and hope partner can preempt.
CRASH is a method to show all 2-suiters. I won't specify the length/strength requirements. Let vulnerabilit