Hello Ryuken,
I'm not an Onmyouji but I know some protection prayers against demons.
I work with Archangels, so try evoking a deity of light to protect you, that's the principle.
The power of words is better when they come from your heart, so try reading about archangels.
A simple protective spells is to draw a pentagram in a paper and visualize light.
Also salt is useful. Hope it helps you.