Visit your local Model Railroad store and see what they got in stock.
I like to build my trees from wire bundles/wire rope, they are sold over here in different length and thicknesses.
What you do is pull Wires(Twigs) or small bundles of wires(Branches) off and position them, of the sub-bundles you can pull smaller bundles or single wires to make smaller branches and twigs.
Very easy to position, putty to add volume/texture if desired, prime, paint and add flock.
I have even made a 1/8 cascading Bonsai using this method for a Diorama, it really allows you to get creative and position everything nicely.
Hope this helps.