Yep Jake and I've mentioned this one a few times. You can often find an older (and actually better quality) artificial tree at a yard sale. I find some of the older ones actually have more "needles" on them, thus appearing as thicker trees when you are all done.
The older ones I've used have twisted metal that the "needles" are wrapped into, so I have found a hack saw necessary to cut the branches down to tree height. I have experimented with trying to glue Lifelike Grass to the branches, but haven't found a glue that holds the grass material for any great length of time without the grass coming loose. I tried a spay glue made by 3M and it worked good initially, but the grass soon came loose.
But I have spray painted them for greater variety. I start with brown paint right up close to get the color to the twisted metal. Then I use various shades of green and blue to do the "needles" spaying that color on from a little more distance to get the color on the outshape of the tree, while retaining some brown on the metal core. Of course, I do this after I have shaped the "needles" so that I have some pine trees of variety of appearances.
I tend to use my better looking or shall I say more detailed trees up front, and then the artificial tree pine trees for the back ground. And as you said Jake, you can made some pretty big trees, which are nice to have around the layout for variety. Or you can put a taller pine in the center of some smaller more detailed trees.
I got a half dozen plain pine trees, but with flocking on them, sold at RiteAid with their holiday decorations for half off. I've discovered a trick to help these trees retain their flocking material. This goes for hobby made trees from other companies. I make up a mix of watered down wood glue, similar to what I use for gluing down ballast or scenic material. Then I soak the trees in that for 5 minutes or so to let the glue soak in. Then I put the wet trees in a pie tin and allow the excess glue to drip off, turning the trees gfrequently to allow equal excess to drip off all sides. Once the majority of glue has dripped off, I will speed the process up and either put them out in direct sun (in the summer) or use a blow dryer.
I've had good luck with this and it does keep the flocking from coming off, which without doing I found does happen over time. I've also done this to my LifeLike "lollypop" types of trees (spring trees, apple trees, fall foilage trees, etc). I got a whole load of them very cheaply years ago when a Woolworth's closed. I also take those and shape them a little bit. I've also removed the plastic base and after some reshaping, will glue one tree on to the top of another matching tree to make a much taller one. I also replace the plastic bases of some trees, using dried out real pine branches taken from tossed out real CHRISTmas trees. I'll drill a tiny hole into the top of the branch and insert the tree into that.... gives a little more height variety.
Years ago at a pet shop I found an aquarium decorative plant I think was called FoxFir or something of the like. I was kind of a branchy looking plant that was colored various shades of brown. I use this on my layout, cutting them down to a couple inches in height, and then placing them in bunches close together which gives the appearance of smaller leaf-less trees. What I like is I can get these up close to the track and because they are soft plastic, there's no damage to trains or trees if they get hit by an engine or unusually wide car.