If you're inside the enemy's WEZ your safest bet is likely to launch and then turn cold. That shot will have a lower PK due to lack of initial guidance, but if it can force your enemy to go defensive you can then decide to re-commit and get in position to launch a second missile with a high PK in the no-evasion launch zone.
Outside of the enemy's WEZ you can crank to provide guidance until the missile goes pitbull, or even fire off a follow-up shot as you enter the WEZ and then turn defensive.