Sorry, i forgot all about this!
I heard from the "tree maker" Gregg Stoll and here is what he said about making those slash pine trees (as they are called in Florida):
"As far at the pine trees go, they are indeed Scenic Express Super Trees, N-scale. I prepped them per the instructions that includes soaking them in mat medium (I soaked them for at least a day to make them really limber) and then hanging them on a line with weights attached so they dried fairly straight. I then used a sharp blade to selectively prune them. The branching is opposite, so in most cases I also pruned off one of the opposite branches. I also worked from prototype tree photos to get the branching to look “right”. I then used some brown fleck-stone spray paint (the finest I could find, some is pretty coarse) and sprayed the trunks at an upward angle from the bottom. I then took a 1 pint plastic container that had a lid on it (like the kind the egg drop soup comes in) and cut a small hole in the center of the lid. I mixed up some fine turf and static flocking of different colors and put it in the container. I took the trunk and holding it horizontally I rolled it in a container of mat medium so only the tips of the branches were soaked. The trunk then went thru the hole in the lid and I snapped it on the container of flocking, held it horizontal, and shook it around. Then using my fingers I spun the trunk making the static flocking point outward. Onto the line they got hung again, until dry. One last light spray of mat medium to set it all, let them dry, and plant."
hope that helps!
my best,
Jan