Go to the Tunnels Waypoint [&BF4AAAA=] in Skrittsburgh Center (in the center of Brisban Wildlands) with a couple of Sealed Package of Snowballs. Unpack one and throw the snowballs at the friendly Skritt in the area. Since they don't attack back like enemy Skritt you will have time to use all of the snowballs spawned. Friendly Skritt don't fall down when hit but you will notice your achievement counter going up. Use the second package and you should have enough hits to get the achievement.
Much easier than trying to hit them in the Dolyak escort in Divinity's Reach :)
Attacking friendly Skritt doesn't seem reliable. When I wrote this I was able to get all 10 hits with 2 bundles, today I could only get 5 hits with about 10 bundles. It might be more reliable to go to Akk Wilds [&BEIAAAA=] and throw snowballs at the enemy Skritt in the area. Hitting them with snowballs doesn't seem to agro them if you stay far enough away to not agro them via line of sight.