I copied the strategy used by elpro4 in their previous world record of attacking Prussia's spherelings and such, but I improved the end of the run by declaring war on Denmark before becoming a GP, so that by the time I became I GP I could just add the sphere war goal and immediately make peace. This could be several months faster with better luck regarding Spain and Ottomans, since the time it takes to become a GP largely depends on how much those two end up trading the 8th rank between themselves or with you.