The function is to slow down the rate of water loss, now that all the "pipes" have been cut open. Of course, it's your hope to reduce end cracking. As DP says, latex paint, wood glue, whatever is lying around in your shop that form a fairly waterproof layer.
The guys in the Diamond Willow furniture shop don't care. They harvest 4-5 cords of 8' sticks in the spring when the sap is running. Peel all the bark, no end sealing at all and into the bins for 2-5 years.
They expect up to 12" cracking. Far faster and cheaper in the long term. The bark? That's a 3/4T pickup, loaded.
All the KD lumber that I buy is end-sprayed with green or blue paint stuff.