I can't speak for AMT base, but for what value an anecdote is of, I know of a person who tripped after handling strong (very strong) psilocybin mushrooms firsthand, being present at the time. Pupils were dilated significantly, and the person (although a manipulative, psycho, borderline, crowbegat gutterfuck and prone to being economical with the tr..a lying bitch) claimed to be tripping. In this case believable as it corroborates my own experience with the same batch of mushrooms.
We had a small harvest of Psilocybe cyanescens at the time, and shared the task of cleaning the crap off them and laying them out on sheets of wood-backed Al foil to sporeprint so as to weed out any deadly, amatoxic Conocybe or Galerina specimens. They were somewhat moist at the time although not wet.
By the time I was but a small part way through wiping the muck from the caps of my portion of our find my vision started to weave, my pupils were very dilated, and I was feeling euphoric. And it went from there. By the time I was finished, I was at a ++ 1/2, and it was quite unmistakeably active.
I would imagine a more lipophilic drug, such as a freebase tryptamine (lacking the polar 4 substituent of psiloc(yb)in would penetrate the skin with greater ease than would a salt.