my bet is using the bijuus and the jubiis power... madara can have all the power in the world. and NO, EMS, i think cant grant abilities...
well, im no expert but let me do this the best i could... first of, madara told the kages that the SO6P created a new jutsu/seal that is used today (host system) but no one really knew how except akatsuki...why? coz remember madara told kages that within the shrine of the uchiha lies a stone of some sort that only this with ocular powers can see, with levels of knowledge unique only to each... madara got hold of the rinnegan so he has the best of all info that one can get, directly, from the SO6P...and that made me believe that madara knew of "that jutsu" (seal) that the sage made as inscribed in that stone, so madara knew how to control the juubi (using the seal/"that jutsu")... why in the first place will madara be bragging about it when he doesnt have the idea how to control it...but, theres a but, he first must accomplish the moon eye tech so he can genjutsu the whole world and order them to "give me ur powers" (dragonball style, i knw its crazy but..) so that madara can have the power requirement necessary to control the 10 tails... But, a second but, madara knew that somehow the blueprint/key for the original seal that the sage used must be in one of the bijuus (obviously its in the 9th, coz everyone knows the 9 tails is the hardest to tame) that's why, madara made sure to take care of the 9 tails, not even injuring the host it came with. remember the last 7 was almost killed, but naruto was spared ("special jiki" after,all -pain)? coz madara knew that the most powerful of all the seal was in the fox, this seal is even capable of controlling the 10 tails...
Therefore, i believe, with this SO6P seal that naruto has now, he can controll pretty much every one of the bijuu including, probably, the juubi...
add: to those who might ask why the seal used by the SO6P is similar to the 4th employed (spiral thinggy) to seal the fox (but the 4th made sure that some of the chakra will leak out so that naruto can "get-the-hang" of the fox's chakra). my simple guess is that the 4th had access to all the scrolls within the countless number of scrolls the konoha have... also, you should understand the konaha's founder was that of the descendants of the sage and that madara also stated that the host-system seal was passed down thru generations in secret...