I have 3 brokerage accounts but my living expenses come out of the largest one- every 4 months I call the broker and tell him how much money to send, which I then deposit to my USAA account. USAA is my only checking account.
Because I'm a retired actuary, I'm a numbers person and am very Excel-friendly. I keep an Excel checking account registry but have "buckets" for categories where payments are irregular, such as medical expenses and property taxes, and add fixed amounts to them each month. The difference between the balance and all of the reserved amounts is what I have left to spend.
I also track my expenses other than cash in great detail. Pretty easy since I use the Fidelity credit card 99% of the time and the rest comes out of a single checking account. (Cash expenses, in general, are negligible.) I find it interesting and it helps me see where the money is going and how I'm doing compared to previous years. Just updated for March and found that, despite spending over $1,000 on jewelry on a trip to India and Nepal, my expenses are still behind the total for March, 2017 because I had heavy expenses on home improvements (window replacement plus plantation shutters) early last year!