I just now figured out that, to use a corner finisher after a match, you have to "trick" the system by keeping your opponent in the corner. This is obviously easier said than done, since I noticed a weird pattern in the mode: When you do get your finisher, your opponent no sells the whip, which instead can lead you preforming your front finisher instead. Once you do the above method, you CAN do a corner finisher like the "Corner Front Dropkick", or the "Slingshot Leg Drop Guillotine".
PS: I don`t have a image on hand, but i will take one later when i play again.