Protect your fingers and control the split cut.
Add a strong clamp like this if you need more pressure than just the clothes pins. I like clothes pins for speed, easiness and because the pressure is directional from two sides, which is perfect for the cleft/wedge graft. You can also quickly remove them to check your graft and then clamp them back on.
Cara Cara orange graft with foil protection from the Phoenix sun. Sometimes I have to use a ziplock bag to protect the new growth on the scion from being dried out by an early April heatwave here. Hot dry desert wind is not my friend.