I'm not on T yet (hopefully October 8th!), but I've been taking different transition herbs. Most recently, I've begun using a Horny Goat Weed (oral) spray. It helps with blood flow down there. Since I've started using it, my little guy definitely gets hard like the real thing, and has even grown the slightest bit, and even though I'm still very dysphoric about that whole situation, it helps just knowing such a thing is possible. In my teens, my libido was sky-high, but even then the thing never got hard, and was always just kinda barely even there. I'm still going to be very dysphoric for a very long time, but I've gained a little bit of confidence for what the future holds, just from my pre-T results.
From what people seem to be saying, when you first get on T, your little guy will hurt and ache from growing, so you can probably expect more sensations from that thing than from your extra hole. Just try not to worry about it too much, and focus your energy on the positive changes that will be happening to your body as a whole once you start on T.