Alternatives to expensive advesives - Model Railroader Magazine

I'm fairly new at making model scenery, and by fairly new I mean I just bought a bunch of turf and clump foliage products from woodland scenics and have only a vague idea of what to do with them. I've experimented with a couple things that turned out fairly nice, but I'm finding my lack of various strong adhesives to be fairly limiting. All I currently use is PVA glue (elmer's white glue), which I apply to clump foliage before adding it to tree branches or on the ground as bushes, and a 1:1 water-pva glue mix which i spray on surfaces with a spray bottle before spreading fine and coarse turf, and which I spray liberally on the whole thing afterward. I find myself thinking that things would be easier and faster if I had some of the various (rather expensive) adhesives that woodland scenics sells, such as hob-e-tac, for use efficiently attaching foliage to trees, scenic cement, to use instead of the water-pva glue mix for the same purposes, and scenic glue, to use instead of standard pva glue.

My question is: are these adhesives actually necessary (I'm somewhat doubtful about scenic glue and scenic cement, are they really just pva glue and watered down pva glue, respectively?), and are there cheaper alternatives?