Regarding the homemade trees:
I purchased a 20" x 30" filter material at Walmart, it's called "Natural Aire", it's dark green, pretty stiff durable material. It's fairly dense, around 1/2 inch thick.
The trunks are Balsa, I purchased a 1/2 x 1/2 x 36 inch long stick, used a small Block Plane, coarse file, to get it tapered. Then used a coarse Zona Saw blade to scratch the grooves into the bark.
For the most part, I followed the ideas in these two Youtube videos:
https://www.youtube.com/watch?v=9wdSKMOV8dY
https://www.youtube.com/watch?v=Hztif1KoJ-g
I like the furnace filter material better than what's described in the videos above. This material is pretty tough fibers and you can "tease it" and pull it apart to make the tree more "airy" without the material completely disintegrating in your hand. You do have to pull off the re-inforcing nylon screen on the back, but it pulls off without taking much material with it.
On the 2nd the a 3rd tree, I decided to start with pieces that were roughly 3 inches and 4 inches in diameter, approximately circular, then start "delaminating" the pieces so that they go from 1/2 inch thick to 3 to 4 inches thick. After some practice, it takes about 5 minutes to delaminate a piece, and it takes about 3 to 4 pieces to complete a tree that is 12 inches tall. This is probably the most important step in the whole process ! You want to thin it out more than you think you need to, as adding paint, needles, and putting it back on the main trunks tends to make the tree more dense again.
Once you're satisfied that you have teased this out enough so the tree branches aren't so "dense", go to next step.
Twist the trunk as you insert into this material.
I glued them on at this point with Carpenters wood glue.
Once it dried, I went around with a scissors and cut some of the ends where there were too many fibers all the same length. Then, I painted it with Rustoleum Camouflage Brown.
Finally I applied Gorilla Spray Adhesive to the branches, and shook 2 MM static grass. There's nothing to attach the grounding clip to, so I used my Noch applicator to get an even flow of grass, but it was not energize. If you don't have an applicator, you can shake it through a sifting screen.
I did set up a corrugated cardboard shelf, and held the tree under it so I could keep the spray adhesive on the ends of the branches, and try not to coat the main trunks.
One last finishing step: I sprayed the trees with extra hold hair spray as small amounts of the fibers were falling off. Also the hair spray allows you to "spot" apply additional static grass to any bare areas without using spray glue over the already applied tree.