...then drive the bolt loose with one of the sharp bills by tap-tap-taps with your favorite hammer. Drive at an angle, pushing on the rim of the bolt outside the star-shaped socket. Like if it was a wheel and tire you'd hit it on the part that says Goodyear and at an angle to turn the tire lefty-loosey.
Hammering on a punch in the bolt socket is also good to help loosen it. The punch has to be sharp enough not to damage the splines. You are trying to shake it loose.
Having a good T27 made out of quality steel is also important, the cheap ones are made out of cheeto dust or something. Although this can mean the shank will twist before it destroys the bolt head, but you have to notice that and stop.
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