If you search RC for 'cycle", many people do it that way. Get a 30 gallon brute, live rock, power head, skimmer, salt water. When you cycle the tank , you are not cycling the "Tank", you are growing bacteria on the innet porous surface of the rock, that feeds on the die-off that happened during rock shipment and transport. Generally cycle is needed for 2 reasons:
A. your rock had dead tissue (99% of the time you had to transport it from lfs to home) and bacteria may not be plentiful enough to consume all the amonia/nitrites available.
B. you have dead rock and you need to seed it so that it can handle your bioload.
So there is no point to get waste water since liverock has all the bacteria it needs, just have him toss it in a dark container with a powerhead and a heater and it WIll start the cycle as long as when transported after, rock isnt dry/cold for prolonged period of time.
In terms of 20-48 hr cycle, there is no such thing, however, if the rock is from a cycled system and was properly transported, there is no cycle generally needed. Ammonia may spike slightly and go away, but that's about it. Its just like moving from one container to another.
here is an article By Dr. Cow with a timeline diagram:
click me
So my buddy Dan who introduced himself on here a cpl weeks ago, got a used 29g Biocube off of EBAY. He asked me if he could get a container, add some live rock to it with some of my water change waste water and put that in his tank when it arrives, resulting in a shorter cycle. Is this possible? I don't really think he should be trying to rush anything with this hobby or this soon into the hobby but I can understand his desires lol.
So in summary, can he get a cycle started in another container? I'm guessing no.