These look like good fantasy or alien trees.
Coated in glue with green wool wrapped around tightly, then brushed once dried, may look good for fir trees.
But for realistic cheap trees use dead bushes.
I saw an article.., some where, where a chap and his pressganged lot would collect a certain bush each year and dry and paint and flock them in bulk for his railway layout.
But most bushes will have tree like bits.
Glue on some bits of steel wool or lufa for finer twigs and then paint and flock.
Something like that.
Or just pick up an old plastic Christmas tree at a garage sale.
I even glued three of these tree ends together, then one on top for a larger scale tree.