You will be OK if you connect a freshly charged battery as instructed and then run a few short tests without disconnecting the battery. Your ESC must use the initial voltage of the battery as a starting point to calculate LVC (low-voltage cutoff). During these brief runs, you can make your current measurements. There are many inexpensive multimeters that can measure 10 amps continuously and up to 20 amps for 15 second intervals. That might do the trick for you if your current requirements are in this range. A dedicated wattmeter is probably the best solution.

Without a meter, you should be OK if you use the setup recommended by the motor's manufacturer. It might be a good idea to use one prop size smaller initially, just to be on the safe side. As you hold on to it (hold on tight and anchor everything behind the prop ) when you briefly run it up to full power you'll get a very good idea if you have enough power for flight. See how warm the motor gets after these runs. You want to avoid very high temperatures that can damage the wiring insulation and/or the magnets. During the first flights, manage the throttle for comfortable flight and reasonable duration. If your easily getting 10 minute or longer flights, you're probably in the ballpark, and you can make incremental adjustments to enhance performance.