If you have the bolt out already (duh, right?) The fastest and safest way is with the headers OFF the engine is to use a block of wood and a dead blow hammer. Simply lay the headers on a soft, scratch proof surface, like the lawn, some carpet or a bunch of towels. Place the block of wood over the end bell holding it perfectly flat and whack the snot out of it. It normally takes one really well executed smack. then they slide right out. I normally hose them down with Aerokroil or PB Blast first.
Don't hit your fingers. ..

GT