A simple method to make a model conifer tree is to pick some buddleia flower heads once they have bloomed. (You'll probably get in trouble if you try it sooner!) But leave it too late and they'll go to seed.
Don't forget that you will need to 'cook' them to kill the bugs and micro-organisms.
Then steep them in a warm water/pva glue mix (4/1) for around a half hour.
Upon removal, roll them in a relevant flock.
And lo, there is a reasonable background conifer tree. Very useful if you need a forest!
Cost: Several trees to the pound or dollar.