I know that you’re more skillful than me, but I wanna share my little experience…
I’ve noticed that is easier for me to charge the SIgil when I have a natural connection to an entity.
I can charge Azazel sigil in a snap, while it takes 10-15 minutes to charge Lucifer Sigil or other entities.
With Azazel has been easy and quick since the first time .
It makes sense that it would be easier (more natural) for you to charge one to work with an entity that you are more familiar with, and/or have more experience working with. The entity you choose is of course part of your intent, and familiarity should make all aspects of the exercise flow more smoothly.