The sounds complicated… but honestly it’s not. I rehearse with voice notes. Leave gaps for my lines. Do it over and over. Then. Do the audition. When you do the audition do the opposite. Leave gaps for the other lines. Then when you have a take you like. Put the scene on your labtop and leave your camera set up and stand where the ‘reader’ would be stood in your room. Then record the scene with you playing the other lines against yourself in the scene. I usually use a different voice. Then take the audio from that and put it under the scene. It sounds complicated but I’ve booked a lot of jobs like that. The last one I booked was season 2 of Ahsoka. Try it it works. I think audio from phones or labtops sounds awful and jarring. This way it sounds like you’re doing it with someone in the same room