Seems like you have choices: one is to let the fusee itself limit the current, which means it will blow very fast, unloading the NFET quicker. Another is to use a series resistance to lower the available current, but wait longer for the fusee to blow. Another is to lower the supply voltage from 12V to say 6V, and that will lower the current, but take only a bit longer.
If you are setting these off manually (with a switch and battery), what do you use for voltage, and do you put resistance in?