so this one requires almost everything to be done before you even unpause the game before you start anything else reduce relations with Prussia so that you can justify on them later and then form an alliance with France and make sure to accept all alliances from your sphere-lings

before you justify on Prussia make sure to change your leading government to the neo-absolutists as they give you +10% justifying speed with their jingoism

on jan-16-1836 you can start justifying on Prussia just go for Prussian Wurttemberg and begin to mobilize your forces and make all the artillery that you can

the next part just comes down to luck and you have to hope you get as many events as you can that speed up your justifying time so this might take a pretty long time and a couple of runs to get

declare war on Prussia try to take berlin and destroy as many units as you can until you're able to make peace with them then you're able to form SGF