You are correct with the misting the water/glue mixture down. The way I did it was mist the ground cover that's stuck with the paint, than re-sprinkle with another layer of "grass". Re-mist the new layer of glue and let it dry. Once it's dry, it will feel kinda like velour, but the ground cover will stay put. You really need a bottle that mists though. Too much spray pressure will blow the "grass" around.
There's plenty of trees on the bay. The bulk purchases work out the cheapest. I didn't have much luck with the Woodland Scenic kits. But I probably didn't use the correct glue, and the kit was older and the clump foliage was one big clump.

The "we honest" trees are kinda scrawny and on the short side, and your purchase may eventually lead to..ahem... enlargement spam in your inbox, as they have sold my email add'y to a few Chinese Phamaceutical companies.. Check out trees at your local HS first, and compare prices and products on the bay. Then determine which is more cost effective. You'll find what you're looking for!!
The track looks great Rick, and it'll be fun to follow along as it progresses..

