Andrew,
Repitching is done with a pitch gauge, heat gun and work gloves. The basic process is to set the pitch gauge at the 70% station to the new pitch you want and lock it there with a small clamp. Next, put on your gloves (these should be heat resistant like leather work gloves) and heat the inner 1/3 of the blade, you need to rotate the prop top to bottom to evenly heat the blade. For IC props you need to heat for 5-7 mins, for electric props heat 3-4 mins each blade. You need to heat soak the blade so heat and let it sit a minute then resume heating.
Once the blade is heated you grab the hub and twist the heated blade in the direction you want the pitch to move. Sometimes you need to do this several times to get the pitch where you want it. The IC props take more heat and a lot of twist force. It takes a few tries but you will develop a feel for how much heat and twist you need to get the blade to move.
BTW, you can also re-pitch wood props the same way.
Best, DennisT