1. Get pissed about how much the grading fees are. 2. Cross my fingers for the grades.
Seriously though, overnight/priority shipping with USPS or FedEx AND insurance.
There are a few important things with the insurance - get private insurance before you mail the package. USPS and FedEx will sell you as much insurance as you want to pay for, but I have read multiple times on Net54 that they won't honor it.
For independent insurance, many here, including myself, use Collectables Insurance Services (
https://collectinsure.com/). They have shipping rules you have to follow based on the amount of the package. And if the total is more than the blanket policy will cover during shipping, you can buy separate, additional insurance (up to very large amounts of coverage) through them that covers things during the single shipping period.
Also, assuming they are insured, make sure you have good scans of everything you mail before you send them otherwise you are going to be in trouble if there is a challenge to your claim.