Drafting is waaaay less common to come into play than whipping.
I recall this guide and think that most mechanics are explained correctly there:
https://www.civfanatics.com/civ4/strategy/military/drafting-for-fun-and-profit/
The key thing to focus on is the completely crazy production potential when drafting riflemen (last unit that requires only 1 population).
With a granary, you need about 15 food to grow from pop5 to pop6, and you get a rifleman worth 110 hammers.
Thats 7.33 hammers per food which is completely off the scale!
Since drafting costs 3 unhappines for 10 turns which stacks, it's hard to draft alot... Unless you have a big empire that is.
If you have 30 cities, you can draft 3 units per turn continiously.
Having a globe theatre city helps alot, that city can be drafted every turn w/o unhappines that leaves you with 20 cities if you want to draft continiously.
But in real play, thats quite uncommon. It's something that can happen lategame though, but the purpose off all that horde of low-xp rifles far from the front are not so much to participate in the fighting, but rather to bump up your own power rating, making capitulations easier.
When it comes to drafting, It's almost always about riflemen, you almost never draft anything prior to that, and you seldom draft after that.
I tend to think about drafting when I'm stuck with a small empire with little land, where I need to have cottages on the few precious tiles I have available. In that case I will have a hard time to whip out alot of units.
It's usually that I draft most cities 2 times, then thats it. But with a 5 city empire thats still 10 rifles which can play a crucial role at the initial phase.
Another trick I have utilized is to draft a marginal bordercity mercilessly, keeping it alive with mass military police with herarditrary rule.
Then I let my foe conquer that city to place his stack inside for me to shoot like fish in a barrel with cannons afterwards. That conquest clears all draft anger.
Also works to just gift the city away right before declaring, and then recapturing it with a chariot the same turn.