ALWAYS - sand the prop edges smooth before balancing the prop - it will not hurt you unless you put your hand in it from the wrong direction when running at high rev. Getting to the prop from the back side when adjusting is only scary as the prop is pushing you finger away. If it "bites" when flipping it is not dangerous - only telling you one of two things.
- It has to much fuel - I will normally pull the prop one turn with the prop in my hand before giving it the start flip.
- You are to slow to get your finger away - the prop is not mounted at the right angle for your flipping.
Or use a short piece of garden pipe to do the contact when flipping - chicken!
I am normally using an anti corrosion spray 5-56 or whatever number your favorite brand has to conserve the engine.