That is the easiest way to do it!
Remove the side plug, fill from the top and go real slow on the last little bit so you don't overfill it, and if you do overfill let it sit with the plug out so it dribbles out to the right level.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-