How can you offer free express shipping upgrades?

Hi, hoping someone can answer this question? We are running a Valentine’s Day campaign and want to entice customers via an express shipping upgrade promotion to subscribers.

At the moment we offer flat rate $10 / free $100> and also express shipping $13.

Any advice would be appreciated.

James

Would love to know the same. Currently, we have to offer a 0.01 discount to apply a shipping upgrade and its confusing for the customer as it doesn’t change the shipping options in cart. Feel like there must be a better solution?