How do you keep up with water volumes?

So many problems with my first AG batch that were simply due to improper amounts of water being added to the MLT. The 8 gallon kettle has no sight gauge, so I poured in 5 measured gallons, found that the level is 3" below centerline of the top rivets, and estimated from there. If the MLT needs 5 quarts of boiling water - not 4 or 6 - how do you know that's what you poured? Is there a set of insulated measured containers that I could use? Metal 2 quart pitchers transfer the heat to my hand too fast, and plastics just slump. Maybe Pyrex - like a coffee brewpot? Advice would be much appreciated...........

I use a plastic gallon jug and a Pyrex quart measuring cup for initial water volumes. For measuring volume in the kettle I notched my large stainless spoon at 4 thru 8 gallon in half gallon increments with a dremel tool.

I use a piece of CPVC pipe that I've marked in gallon increments with a Sharpie.