You need to get your hands on some natural fiber air filters. These are becoming more and more difficult to acquire as most vendors are moving towards synthetic materials. Fortunately you can still get the filters from Rona Revy. They're priced $5.53 for a 20" x 25" x 1" pad. It's manufactured by American Air Filters and the model is called Cut-N-Fit. Canadian Tire sells something similar, but it's unsuitable because the fibers are too densely packed. You want the fibers to be loose.
Taking the air filter, you'll need to cut it in half length wise so you'll have two 10" x 25" x 1" pad. Now cut 2" x 10" strips. Then take those strips and cut triangles so the base is 2". You'll want to take the triangle and cut circles out of the pads. Now apply glue on the skewer and push the circular pads you cut from the air filter onto the skewer. Biggest circle first, smallest last.
Before you can assemble everything together you need wooden skewers you need to stain them black or brown. I used acrylic paint and thinned it down with some water before applying it onto the skewers. The length of skewers depend on your scale. The club's layout is HO.
It's recommended that you make trees of varying height. Al described to me about perspective and placing shorter trees in the background gives the impression of distance. I never realized this until he explained it to me. I've got a lot to learn still and a bunch more of trees to make before the next step. About 50 more trees to go. Once the white glue dries, it will turn clear. Then I can paint and sprinkle some Woodland Scenic green fine particles to make the trees look more realistic. Although, I'm considering using some form of clear lacquer or shellac and thinning it down to a very viscous liquid and dipping the trees instead of spray painting. The paint is only used to cause the Woodland Scenic material to adhere to the fibers.
