well, i scared Prussia power, leaders and MP mostly, and send to north front best leader. But after all i could manage Prussia activity in the region, while Austrian assaults by Franz were strong - he could assault large fort by 40-50K regularly.
So at second part of war best leader went to south, and got success to kick Austrians back (with Spain activity in this region too, despite their poor leadership) and conquer Bern even. Weaker leader made successful defending vs Prussians and even make nice positive battles using tactic. Coastal attacks and assaults had to be done without leader at all - i didn`t have third leader above 3-2-2 orig.
And of course i managed to create situation to use attrition vs you.