This breakout board will solve all your power-monitoring problems. Instead of struggling with two multimeters, you can just use the handy INA219B chip on this breakout to both measure both the high side voltage and DC current draw over I2C with 1% precision.
The INA219 is a current shunt and power monitor with an I2C- or SMBUS-compatible interface. The device monitors both shunt voltage drop and bus supply voltage, with programmable conversion times and filtering. A programmable calibration value, combined with an internal multiplier, enables direct readouts of current in amperes. An additional multiplying register calculates power in watts. The I2C- or SMBUS-compatible interface features 16 programmable addresses.
Board is equipped with SparkFun qwiic compatible STEMMA QT connectors for the I2C bus so you don’t even need to solder the I2C and power lines. Just wire up to your favorite micro using a STEMMA QT adapter cable.
Key Features

0.1 ohm 1% 2W current sense resistor
Up to +26V target voltage
Up to +-3.2A current measurement, with +-0.8mA resolution
Note: The terminal block included with your product may be blue or black.
This board/chip uses I2C 7-bit addresses 0x40, 0x41, 0x44, 0x45, selectable with jumpers

STEMMA QT / Qwiic 4-pin 1mm Pitch White Female Connector Cable 150mm Long – Both Sidecan be purchased seperately.
Resources

INA219 Datasheet

Eagle PCB files for the INA219 breakout board

Arduino driver library

Data Sheet for the INA219 chip

Fritzing object in the Adafruit Fritzing library

Product tutorial

Adafruit INA219 Current Sensor Breakout

Pro Trinket Power Meter

Low Power WiFi Datalogger

Build a Cloud-Connected ESP8266 Power Meter