Its just trail and error ... they do perform much differently IMO.
I find the 306 pretty much worthless except for the 2Ω which you have.
I enjoy that atty quite a bit.
I give them a good soak with about 7 drops and let them sit for 10 or 15 min
Then a quick little squonk and I'm off.
I feel like they need less juice than a 510 to perform properly ....
I cant make a 1.5Ω 306 work to save my azz!
The 1.5 needs more juice to not burn, but then your at the flooded stage.
Stick with it, it can be a great atty once you get the hang of it.
I tend to do the blind squonk with 306 and cartos ..... but I watch for the juice with 510s

(Blind Squonk = squonk while drawing air without the button pressed)
Once you feel any resistance in the air flow stop squeezing and you should be good.