Renting a docker is taking 2-3 min until is operational.
One docker is containing max 16 cards.
So having something automated for a bigger number of cards, should take 5 min until can start processing.
I don't know where you rent your docker, but it normally takes less than a minute to start it up.
Automating it does not really add much time at all. If you need to execute a single command to get things up, that's like another 10 seconds.
If you have longer times, you must be doing something wrong and there is a lot of room to improve.