figure customizing info

What up football people! Hope you all enjoyed the draft, I sure did, GO LIONS!!!

Anyway I've gotten a few custom figures from a few of you guys and I want to make some of my own. How do you guys shape the arms, legs, etc? I've got hobby putty to fill in cut gaps but I'm not sure the best/most effecient way to cut parts off? Hot razor knife? snips? any help is much appreciated.