How do you actually practice system design without a whiteboard partner?

Every guide assumes you've got a friend or a paid mock partner to bounce ideas off, ask you the follow up questions, push back when your assumptions are wrong. I don't have that right now. Been trying to talk out loud to my laptop camera and review the recording after, which is uncomfortable but at least shows me where I trail off or hand-wave. Curious if there's something better than talking to yourself that's actually worked for people prepping solo.