Mixing containers, and why shape is thermal
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Tall and narrow is the dangerous shape
It concentrates the mass, minimizes the surface available to lose heat and wraps the lot in an insulating wall. That is the geometry most likely to run away. A wider, shallower container with the same volume sheds heat far better and buys working time.
Which means pour promptly, or spread out
Resin left standing in the cup is resin in the worst shape it will be in all day. If a pour is interrupted, moving the mix into something wide is a better response than waiting with it in the cup.
Graduations have to be readable and durable
Measuring by eye against a molded graduation is normal and the markings have to survive the contents and the wiping. A smooth-walled container with nothing on it is fine if you measure by weight and useless if you measure by volume.
Weight beats volume where the product allows
A scale is more precise than a molded line, it is faster, and it removes the meniscus judgment entirely. Use whichever basis the product specifies, and if it gives both, weight is the easier one to get right consistently.
Two cups is standard practice
Mix in one, scrape it down, then transfer to a second and mix again. It leaves the unmixed film from the first cup behind rather than in the casting, and it is the cheapest fix for patchy cures there is.
Treat them as consumables
Cured residue in a cup contaminates the next batch and cleaning them with solvent is an exposure. Letting leftovers cure solid and discarding the cup is both safer and usually cheaper than the solvent and the time.