I use mostly the 2.4 carts.
Some like the 1.5 carts.
I just load and go.
Never anything special.
I load 0.6 gram use about 0.1 gram then load 0.2 gram.
3 grams per cart is about what I have been getting.
Once again, I think Ataxian has it nailed. Loading and priming 1.5s is the same as 2.4s. By the time you've mastered the 2.4 you should be able to load fully in one shot, priming problems should be history. Otherwise, it's good to remember the heaters are about twice as powerful as with 2.4s. The heat can get away from you much faster, either cooking the oil that's trying to feed or melting the seals around the dry heater. There's just less margins, it's a more powerful tune with all that brings.
FWIW I tend to run the first fill a little longer than the Brother, I'll usually run .3 or so (so I'm down to .2 left) then reload. Truth be known I sometimes cheat a bit and load 'heavy' the first go with stuff I'm familar with, loading up to 2/3 of the gram (shooting for .6). I weigh each vial full, scoop .6 or a bit more into the tool and load the rest next time.
I also agree, 3 grams a cart is good service. Carts are $7 at the local dispensary, I just figure a $2.50 'tax' on each gram. If the taste starts to shift, or feed balks, I'll swap it out early of course. IMO it's not worth fighting a problem cart, I got the sucker to enjoy.
OF