acshrpe,
First, welcome to the gauge. The question was asked, what are you using for leaves, so I won't ask it again. I will make an assumption that you are using something like Woodland Scenic's tree kits.(you mentioned Hobby Tack).
A while back I did demo on tree making, at the local library, as part of an ongoing layout construction demo. I was using the Woodland Scenic tree kits, and taught the following: Take the armatures and form them to represent the kind of tree you want.
The "foliage" provided in the kit is rather too "lumpy" to work with, so I recommended that the "foliage" be torn into much smaller pieces.
I sprayed the armature with 3M Super 77 spray adhesive, dumped some of the foliage in a bag, added the sprayed armature, and "shake-and-bake" out comes a tree, well..... after three or four sprays and shakes.
Once the tree looked "full" enough, I sprayed a coat of Testors Dull Coat to insure that all the foliage would stay where it was( there was still some "fallout", but not bad). the tree was then stuck in a sheet of foam, to allow the dull coat to dry.
The trees sat for a week before the next demo, where I planted them on the layout.
I also showed one tree building method which used furnace filter being applied to the armature. once the Super 77 had set, the filter material was trimmed to a pleasing shape, and then was spray painted with Floquil roof brown. Almost immediately, it was sprayed with Testors Glosscoat, and Woodland Scenics "Coarse Turf" was sifted on. this was repeated about three or four times until the leaves were thick enough, and a filal spray of Glosscoat was added, to "fix" the leaves.
The furnace filter technique was also used to make "leafless" trees, which had Woodland Scenics "Snow" sprinkled on instead of coarse turf. Makes a nice "winter" tree.
Hope this helps,
Pete