Timing cooking: methods / workflow
I came up with a technique one Thanksgiving that I've used for complex meals ever since.

I have three Digital Cooking Thermometer/Timers and a dry-erase board on my refrigerator.

On my dry erase board I draw a table something like this (I don't use the actual headings, they're here for clarity):


Task 1            | Task 2                | Task 3
Baste turkey (60) | Prep green beans (30) | Prep pie (15)
Baste turkey (60) | Prep potatoes (20)    | Turn down oven to 350 (20)
Baste turkey (60) | Cook green beans (10) | Cook potatoes (20)


The numbers in parentheses are the time in minutes. I set each timer to the appropriate time, and cross out each item as I go. The thermometers are positioned directly above each column.

(You can use any timer really, I just like mine to serve two purposes)

It's flexible enough that you can do just about anything this way. You shouldn't feel obliged to use a single column for a specific item, it's unnecessary. Notice that potatoes span columns 2 and 3. 

Clearly this requires thorough planning, but your question states that this is assumed.

I had tried other methods where I planned everything meticulously using the wall time (e.g. 4:30 start potatoes, 4:45 start beans, 4:50 baste turkey, 4:55 resume beans) but this was chaos and you will inevitably lag somewhere which means you're having to adjust your times in  your head on the fly. Not fun.

Update

I didn't make this clear, but you don't need to set the timer to time exactly how long each task will take to complete. You can (and should) include any appropriate buffer time before the next task needs to begin. e.g. In my example above "prep green beans" would never take 30 minutes, likely just 10, but for the timing of my meal I don't want to start my potatoes until 30 minutes later, hence 30m for the green beans.

I'll sometimes also have a timer set for an "idle" task. (e.g. if I don't need three timers for most of the meal prep, but I'll need three towards the end (dessert), then I may set timer 3 for a 60m "idle" task to let me know when to start dessert) I initially overused idle tasks when starting this out (e.g. Task 2: prep gb (10), idle(20), prep potato (10), idle(10), cook gb (10), ...), but this confused the hell out of me and I had timers going off that had me scrambling to see that the next thing to do was... nothing. That's why I started bundling idle time into the previous task.