I think I'm gonna write a little about what I've done, so as to document that it is possible to dominate someone not using anything but communication.
Dulci, my slave in training has been speech restricted. She is not allowed to speak to anyone in public chat or IM without asking for my permission first. And so far, that has worked out perfectly. She told me that it makes her happy, that she can show other people her submission to me in that way. It also makes her seem very humble (which she really is) towards other people and especially towards me.
Dulci again, has to follow me around very close. She's not allowed to stray without my permission and so far that has also worked out perfect (not counting lag). We agreed that it could be concidered an invisible leash, and this way we also avoid any raised brows from nilla people.
I've spend a lot of time speaking to my subs, as I usually do, but we've been focusing on triggers and respond. All my subs agree that following orders, having restrictions (like the above), and generelly pleasing me by their mere presence is a great way to make them feel dominated. One of them (Dulci) even told me she'd love to try that out in real life as well, if she has a dom. Especially the speech restriction has been a joy for her this week. And I realized that even having these conversations is domination. It came naturally to me before, but the experiment has made me think what it truely is that makes me a dom.