This hobby is still pretty new to me, but from what I understand the pre-soak is to allow the overall temperature of your ice slurry to get as close to the ice itself as possible, before agitating the trichomes. I guess the idea is that when you add ice water to your ice, your water is still not as cold as it could be... letting it sit with the ice makes it colder? I'll have to try without the pre-soak and compare, I'm curious now.
Workin on the melt pics, still haven't quite figured out how shoot while smoking as the other pros in this site have!