Just don't do it.
I don't understand why you would take a risk with your chameleons health and well being.
It doesn't matter that you cup feed, he will go down and try to "zap" the substrate on purpose. I have seen baby veileds do it with potting soil, gravel and bark.
Just don't have it!
Some artificial plants are fine. I personally prefer more real plants. A baby veiled will also chew on fake plant leaves. If you provide him with real non-toxic plants then this is not a problem.
-Brad