Any tips on how to wall train trees, such as cornus crab apples and or tropicals

Thought this was pretty good info: http://extension.oregonstate.e...

http://www.bbc.co.uk/gardening...

I know this technique is used often for orchard type trees.
But can any shrub be trained to a wall even with a simple fan shape?
I have plans to make my new property an urban wildlife oasis and want to cram as much as possible onto my lot, haha.

Could one wall train Aesculus pavia for instance? (Interested for hummingbirds and squirrels).
Or Lindera benzoin or even Zanthoxylum americanum for swallowtail host plants?

@PollyDoodle

Havent seen any answers but was also interested as I am also modifying my urban lot considerably. . My thought is that Zanthoxylum americanum (prickly ash) forms thickets and might be unsuitable for training. I too have been trying to figure out how to incorporate them for giant swallowtails. Large container maybe? On the otherhand, I have been toying with planting rue for the same reason. However, it is said to create skin rashes so I wonder how common that is.

Lindera benzoin (spicebush) branches well in all directions so it would be interesting to see if they could be trained. Seems like it might do OK in a pot though. I was thinking about trying it in a container as well. Of all the foodplants usedby spicebush swallowtail, L. benzoin would seem the easiest to plug into an urban lot.

Aesculus pavia (red buckeye) on the surface might seem easier to train though I don't have firsthand experience with growing it that way. I planted it at my folks' house many years ago. It did well for about 15 years the succumbed to some sort of disease.