These are the materials needed to complete model bushes. I use Woodland Scenics Turfs. They are light and airy. Both coarse and fine work well. Two tweezers are needed. One clamp and one regular, the regular to pull the bush off the clamped tweezers. I use cheap hair spray bought at the dollar store. I have a probe or thin stick to help thin the armatures.
I glue the polyfiber to a piece of construction paper. This gives a base to grasp. It also gives an anchor when pulling the polyfiber.
I use Quick Grip to glue the polyfiber to the cardboard. It sets quickly and is readily available.
Apply little dabs of glue to the cardboard. These determine size of the final bush. Tear off a small piece of polyfiber and push it into the glue. I use my own homemade polyfiber. There are several commercially available.
This is the final bush farm.
Cut the bushes from the cardboard. Trim the bases up to the glue line.
Pull the polyfiber out until it forms a bushy armature.
Pour the foam into one of two dishes. These are cheap dishes from the dollar store. Grasp the bush base with the clamp tweezers. Spritz the bush with the cheap hair spray. Dump the foam from one bowl to the other. Alternate dumping until the foam doesn't add anymore.
After the first application examine the bush, if the armature is too thick the foam will "cotton ball". It will not have a delicate appearance. It will need to be thinned. Here there is too much polyfiber showing. It looks like a cotton ball with foam attached.
If your bush "cotton balled" shake off the foam and thin the polyfiber. I have found cutting off the top of the ball with scissors makes it easier to make a good armature. This armature could actually be thinned ever more to create an effective bush. I use the probe to pull the fibers out. What is a good armature will be developed with practice. Save the removed polyfiber and roll it into balls for future use.
Apply the foam to the thinned armature. Spritz it again and let the hair spray dry. This will hold the first layer of foam better. It should look light and airy.
After the first application is dry apply a second application of foam and let that dry. Spritz the bush with a final coat of hair spray to hold the foam in place. Pull the bush from the clamping tweezers with the extra pair of tweezers.
The polyfiber bush has a limitation in size. This was an attempt to make a larger O scale bush. The polyfiber will "cotton ball" at this size and will not support the foam. I found bushes made from faux fur could be made into larger bushes.