I have asked countless times on this forum, to no avail. It seemed like I would have to figure this out by myself. How does Snakespeed expert skill get trained?
The creators of W8 assumed that there would be many battles, taking a very long time, so they gave the Snakespeed expert skill an extremely low amount of rolls for skill increases.
Snakespeed can increase by any action taken by a character during combat (I have seen it increase by characters just defending during combat). Yes, Defend counts as an action.
Knowing this, I fought a few battles against low-level Savant machines, namely, Savant Guards and Savant Troopers. I knocked the group down to 1 machine, and let it batter my Bard in the front, protected by Guardian Angel and Bless.
After 100+ rounds, when the machine passed out, I killed it. Several party members gained skill increases in Snakespeed due to this.
Edit: Nobody cares. Just know that every round is a possible tiny roll for Snakespeed.