To rapid fire or swing the sword just equip any magic that has to charge up. Then just hit the attack, bow or sword, then right after that tap the magic button. Don't hold it just tap. Then just attack again. It takes some practice to get the timing right. It's a slow steady pattern from the magic to the next attack.
i have another tip for fast killing it works great.
if you hit the (X) bottom 3 times is going to swing the sword the same 3 times so when the sword is swiming press the spell bottom to start chargin the spell so when the sword sto you can fire the spell after that you can repeat this many times as you want.