I've been wondering how long the refueling of a rocket, say the falcon 9 takes. That's it.
The difference in loading a flown booster and a brand new booster is the same. SpaceX starts loading RP1 and first stage LOX at T-35 min. RP1 fueling on the first stage finishes around the T-3 min and second stage around T-2 min time. For LOX fueling, they never really finish loading, they will keep topping off the LOX that's boiled off til about liftoff. So it roughly takes about 32 minutes to fuel up the first stage of a Falcon 9.
You can find the times they start fueling in their press kits and they usually explain the entire process in the beginning of each livestream.