Hey Dillon, yes I did use woodland scenic trees. I'm not quite sure what you need to know specifically so I'll try to explain a little bit of everything... Before I get started just letting you know that most of the ideas I got from this site..
How to Make a Diorama
Just click on start the tutorial and go through the pages, it's quite helpful
But anyways, most of the bushes I first applied a good amount of Hob-e-tac glu to the bottom, and held them on their spot for about a minute or so to let the glue set. I would then continue to add more brush and weeds around the area as I did with the first bushes. Then after i was done with a certain area I sprayed the whole aea with scenic cement. And for any underbrush I just used the same method but placed the bushes/weeds under the trees. Also I'm not sure if you glued the trees on with or without the attachable base. My diormama's terrain is so uneven it was hard to find a flat spot to actually make it so the trees would stand with the base on. I tried the trees with the bases for awhile, but finally got fed up with them. I ended up taking a medium sized sewing needle and poking holes in the ground, and simply glueing the tree's base insert in the hole. It works out a lot easier and you dont have to hold the tree in place because the ground does for you
But judging from your pictures you already seem to have a good sense of how to apply the vegetation. One thing I might do, and am actually working on in my diorama, is darken up the areas of the trail where tires and tank treads would have run through. Then go back and add in a touch of growth in the middle section (right in between the tire/tank tread marks) because you always see that little section of growth in the middle of dirt roads.