Never think in isolation. There are others also doing it. How do they do it? Get back to manufacturer. As one aviation cliche says in aviation if you have to learn everything through your own mistakes you probably won't live that long enough. A320 Cockpit preparation takes 5 to 7 minutes, the longest part is the briefing. Interuptions can definitely be put on hold or staggered between the preparations. The CL itself doesn't take much time to complet it should be done without interruption.