I have found a way to download a daily Time & Sales log from my Trading Platform in CSV or XLS format. It is configurable before download on what order it prints and what fields are populated and printed, so that makes things easy. I can also download a CSV or XLS file from the brokerage Website quarterly or by specified date, but lacks the time stamp.Tracking your trades is the broker's job. If they cannot provide you with all the documents you need for tax purposes, time to find a new broker. I would probably kill myself if I had to enter every trade into excel.
Be careful that your deductions are fully legitimate. I don't expect you will be able to deduct much as a day trader. As a passthrough entity I think the main benefit of an LLC is the limited liability.