You'll need:
barbecue sticks
scotchbrite scouring pads

First ( and the most important and delicate operation ) is to separate the scouring pad because it is made of 3 layers.
With your hands ( scissors gives a too regular shape ) roughly cut the layers in pieces of various diameters size.
( I use various Canadian coins as a template )

Please use a dust mask for those 2 operations.

Cut the barbecue stick ( 2.5 " is Ok for N scale ) , sharpen the tip and paint it a dark gray color.

Apply some Elmer's glue on the stick and insert the scotchbrite "disks" in decreasing diameters on it .
And voila ... your conifer is ready.

You can spray the tree with Woodland Scenics scenic cement and sprinkle some mixed turf on it.

Jacques

Looks good to me Jaques! You could forest an entire hillside for not too many bucks!

Ralph

Thanks Ralph for taking some of your valuable time to reply.
Those conifers are not exactly the kind I would put in the foreground of my layout.; I'll make several of them and group them on my small oval layout.
Of course on my 12" X 24" switching layout, foresting "an entire hill" would be quite difficult to do.

Jacques